From 6882a04fb36642862b11efe514251d32070c3d65 Mon Sep 17 00:00:00 2001
From: Konstantin Tokarev <annulen@yandex.ru>
Date: Thu, 25 Aug 2016 19:20:41 +0300
Subject: Imported QtWebKit TP3 (git b57bc6801f1876c3220d5a4bfea33d620d477443)

Change-Id: I3b1d8a2808782c9f34d50240000e20cb38d3680f
Reviewed-by: Konstantin Tokarev <annulen@yandex.ru>
---
 Source/WebCore/rendering/RenderBlock.cpp | 9048 ++++++++----------------------
 1 file changed, 2282 insertions(+), 6766 deletions(-)

(limited to 'Source/WebCore/rendering/RenderBlock.cpp')

diff --git a/Source/WebCore/rendering/RenderBlock.cpp b/Source/WebCore/rendering/RenderBlock.cpp
index c1b3fe154..3ffdef97d 100644
--- a/Source/WebCore/rendering/RenderBlock.cpp
+++ b/Source/WebCore/rendering/RenderBlock.cpp
@@ -25,7 +25,6 @@
 #include "RenderBlock.h"
 
 #include "AXObjectCache.h"
-#include "ColumnInfo.h"
 #include "Document.h"
 #include "Editor.h"
 #include "Element.h"
@@ -38,6 +37,7 @@
 #include "HTMLNames.h"
 #include "HitTestLocation.h"
 #include "HitTestResult.h"
+#include "InlineElementBox.h"
 #include "InlineIterator.h"
 #include "InlineTextBox.h"
 #include "LayoutRepainter.h"
@@ -45,32 +45,41 @@
 #include "OverflowEvent.h"
 #include "Page.h"
 #include "PaintInfo.h"
+#include "RenderBlockFlow.h"
 #include "RenderBoxRegionInfo.h"
+#include "RenderButton.h"
 #include "RenderCombineText.h"
 #include "RenderDeprecatedFlexibleBox.h"
 #include "RenderFlexibleBox.h"
 #include "RenderInline.h"
+#include "RenderIterator.h"
 #include "RenderLayer.h"
-#include "RenderMarquee.h"
+#include "RenderListMarker.h"
+#include "RenderMenuList.h"
+#include "RenderNamedFlowFragment.h"
 #include "RenderNamedFlowThread.h"
 #include "RenderRegion.h"
+#include "RenderSVGResourceClipper.h"
 #include "RenderTableCell.h"
 #include "RenderTextFragment.h"
 #include "RenderTheme.h"
+#include "RenderTreePosition.h"
 #include "RenderView.h"
 #include "SVGTextRunRenderingContext.h"
 #include "Settings.h"
 #include "ShadowRoot.h"
+#include "TextBreakIterator.h"
 #include "TransformState.h"
+
+#include <wtf/NeverDestroyed.h>
+#include <wtf/Optional.h>
 #include <wtf/StackStats.h>
 #include <wtf/TemporaryChange.h>
 
 #if ENABLE(CSS_SHAPES)
-#include "ShapeInsideInfo.h"
 #include "ShapeOutsideInfo.h"
 #endif
 
-using namespace std;
 using namespace WTF;
 using namespace Unicode;
 
@@ -79,46 +88,57 @@ namespace WebCore {
 using namespace HTMLNames;
 
 struct SameSizeAsRenderBlock : public RenderBox {
-    void* pointers[2];
-    RenderObjectChildList children;
-    RenderLineBoxList lineBoxes;
-    uint32_t bitfields;
 };
 
 COMPILE_ASSERT(sizeof(RenderBlock) == sizeof(SameSizeAsRenderBlock), RenderBlock_should_stay_small);
 
-struct SameSizeAsFloatingObject {
-    void* pointers[2];
-    LayoutRect rect;
-    int paginationStrut;
-    uint32_t bitfields : 8;
-};
+static TrackedDescendantsMap* gPositionedDescendantsMap;
+static TrackedDescendantsMap* gPercentHeightDescendantsMap;
+
+static TrackedContainerMap* gPositionedContainerMap;
+static TrackedContainerMap* gPercentHeightContainerMap;
+
+typedef HashMap<RenderBlock*, std::unique_ptr<ListHashSet<RenderInline*>>> ContinuationOutlineTableMap;
 
-COMPILE_ASSERT(sizeof(RenderBlock::MarginValues) == sizeof(LayoutUnit[4]), MarginValues_should_stay_small);
+struct UpdateScrollInfoAfterLayoutTransaction {
+    UpdateScrollInfoAfterLayoutTransaction(const RenderView& view)
+        : nestedCount(0)
+        , view(&view)
+    {
+    }
 
-struct SameSizeAsMarginInfo {
-    uint32_t bitfields : 16;
-    LayoutUnit margins[2];
+    int nestedCount;
+    const RenderView* view;
+    HashSet<RenderBlock*> blocks;
 };
 
-typedef WTF::HashMap<const RenderBox*, OwnPtr<ColumnInfo> > ColumnInfoMap;
-static ColumnInfoMap* gColumnInfoMap = 0;
+typedef Vector<UpdateScrollInfoAfterLayoutTransaction> DelayedUpdateScrollInfoStack;
+static std::unique_ptr<DelayedUpdateScrollInfoStack>& updateScrollInfoAfterLayoutTransactionStack()
+{
+    static NeverDestroyed<std::unique_ptr<DelayedUpdateScrollInfoStack>> delayedUpdatedScrollInfoStack;
+    return delayedUpdatedScrollInfoStack;
+}
 
-static TrackedDescendantsMap* gPositionedDescendantsMap = 0;
-static TrackedDescendantsMap* gPercentHeightDescendantsMap = 0;
+// Allocated only when some of these fields have non-default values
 
-static TrackedContainerMap* gPositionedContainerMap = 0;
-static TrackedContainerMap* gPercentHeightContainerMap = 0;
-    
-typedef WTF::HashMap<RenderBlock*, OwnPtr<ListHashSet<RenderInline*> > > ContinuationOutlineTableMap;
+struct RenderBlockRareData {
+    WTF_MAKE_NONCOPYABLE(RenderBlockRareData); WTF_MAKE_FAST_ALLOCATED;
+public:
+    RenderBlockRareData()
+        : m_paginationStrut(0)
+        , m_pageLogicalOffset(0)
+        , m_flowThreadContainingBlock(Nullopt)
+    {
+    }
 
-typedef WTF::HashSet<RenderBlock*> DelayedUpdateScrollInfoSet;
-static int gDelayUpdateScrollInfo = 0;
-static DelayedUpdateScrollInfoSet* gDelayedUpdateScrollInfoSet = 0;
+    LayoutUnit m_paginationStrut;
+    LayoutUnit m_pageLogicalOffset;
 
-static bool gColumnFlowSplitEnabled = true;
+    Optional<RenderFlowThread*> m_flowThreadContainingBlock;
+};
 
-bool RenderBlock::s_canPropagateFloatIntoSibling = false;
+typedef HashMap<const RenderBlock*, std::unique_ptr<RenderBlockRareData>> RenderBlockRareDataMap;
+static RenderBlockRareDataMap* gRareDataMap = 0;
 
 // This class helps dispatching the 'overflow' event on layout change. overflow can be set on RenderBoxes, yet the existing code
 // only works on RenderBlocks. If this change, this class should be shared with other RenderBoxes.
@@ -130,7 +150,7 @@ public:
         , m_hadHorizontalLayoutOverflow(false)
         , m_hadVerticalLayoutOverflow(false)
     {
-        m_shouldDispatchEvent = !m_block->isAnonymous() && m_block->hasOverflowClip() && m_block->document()->hasListenerType(Document::OVERFLOWCHANGED_LISTENER);
+        m_shouldDispatchEvent = !m_block->isAnonymous() && m_block->hasOverflowClip() && m_block->document().hasListenerType(Document::OVERFLOWCHANGED_LISTENER);
         if (m_shouldDispatchEvent) {
             m_hadHorizontalLayoutOverflow = m_block->hasHorizontalLayoutOverflow();
             m_hadVerticalLayoutOverflow = m_block->hasVerticalLayoutOverflow();
@@ -147,10 +167,12 @@ public:
 
         bool horizontalLayoutOverflowChanged = hasHorizontalLayoutOverflow != m_hadHorizontalLayoutOverflow;
         bool verticalLayoutOverflowChanged = hasVerticalLayoutOverflow != m_hadVerticalLayoutOverflow;
-        if (horizontalLayoutOverflowChanged || verticalLayoutOverflowChanged) {
-            if (FrameView* frameView = m_block->document()->view())
-                frameView->scheduleEvent(OverflowEvent::create(horizontalLayoutOverflowChanged, hasHorizontalLayoutOverflow, verticalLayoutOverflowChanged, hasVerticalLayoutOverflow), m_block->node());
-        }
+        if (!horizontalLayoutOverflowChanged && !verticalLayoutOverflowChanged)
+            return;
+
+        Ref<OverflowEvent> overflowEvent = OverflowEvent::create(horizontalLayoutOverflowChanged, hasHorizontalLayoutOverflow, verticalLayoutOverflowChanged, hasVerticalLayoutOverflow);
+        overflowEvent->setTarget(m_block->element());
+        m_block->document().enqueueOverflowEvent(WTFMove(overflowEvent));
     }
 
 private:
@@ -160,58 +182,19 @@ private:
     bool m_hadVerticalLayoutOverflow;
 };
 
-// Our MarginInfo state used when laying out block children.
-RenderBlock::MarginInfo::MarginInfo(RenderBlock* block, LayoutUnit beforeBorderPadding, LayoutUnit afterBorderPadding)
-    : m_atBeforeSideOfBlock(true)
-    , m_atAfterSideOfBlock(false)
-    , m_hasMarginBeforeQuirk(false)
-    , m_hasMarginAfterQuirk(false)
-    , m_determinedMarginBeforeQuirk(false)
-    , m_discardMargin(false)
-{
-    RenderStyle* blockStyle = block->style();
-    ASSERT(block->isRenderView() || block->parent());
-    m_canCollapseWithChildren = !block->isRenderView() && !block->isRoot() && !block->isOutOfFlowPositioned()
-        && !block->isFloating() && !block->isTableCell() && !block->hasOverflowClip() && !block->isInlineBlockOrInlineTable()
-        && !block->isRenderFlowThread() && !block->isWritingModeRoot() && !block->parent()->isFlexibleBox()
-        && blockStyle->hasAutoColumnCount() && blockStyle->hasAutoColumnWidth() && !blockStyle->columnSpan();
-
-    m_canCollapseMarginBeforeWithChildren = m_canCollapseWithChildren && !beforeBorderPadding && blockStyle->marginBeforeCollapse() != MSEPARATE;
-
-    // If any height other than auto is specified in CSS, then we don't collapse our bottom
-    // margins with our children's margins.  To do otherwise would be to risk odd visual
-    // effects when the children overflow out of the parent block and yet still collapse
-    // with it.  We also don't collapse if we have any bottom border/padding.
-    m_canCollapseMarginAfterWithChildren = m_canCollapseWithChildren && (afterBorderPadding == 0) &&
-        (blockStyle->logicalHeight().isAuto() && !blockStyle->logicalHeight().value()) && blockStyle->marginAfterCollapse() != MSEPARATE;
-    
-    m_quirkContainer = block->isTableCell() || block->isBody();
-
-    m_discardMargin = m_canCollapseMarginBeforeWithChildren && block->mustDiscardMarginBefore();
-
-    m_positiveMargin = (m_canCollapseMarginBeforeWithChildren && !block->mustDiscardMarginBefore()) ? block->maxPositiveMarginBefore() : LayoutUnit();
-    m_negativeMargin = (m_canCollapseMarginBeforeWithChildren && !block->mustDiscardMarginBefore()) ? block->maxNegativeMarginBefore() : LayoutUnit();
+RenderBlock::RenderBlock(Element& element, Ref<RenderStyle>&& style, BaseTypeFlags baseTypeFlags)
+    : RenderBox(element, WTFMove(style), baseTypeFlags | RenderBlockFlag)
+{
 }
 
-// -------------------------------------------------------------------------------------------------------
-
-RenderBlock::RenderBlock(ContainerNode* node)
-    : RenderBox(node)
-    , m_lineHeight(-1)
-    , m_hasMarginBeforeQuirk(false)
-    , m_hasMarginAfterQuirk(false)
-    , m_beingDestroyed(false)
-    , m_hasMarkupTruncation(false)
-    , m_hasBorderOrPaddingLogicalWidthChanged(false)
+RenderBlock::RenderBlock(Document& document, Ref<RenderStyle>&& style, BaseTypeFlags baseTypeFlags)
+    : RenderBox(document, WTFMove(style), baseTypeFlags | RenderBlockFlag)
 {
-    setChildrenInline(true);
-    COMPILE_ASSERT(sizeof(RenderBlock::FloatingObject) == sizeof(SameSizeAsFloatingObject), FloatingObject_should_stay_small);
-    COMPILE_ASSERT(sizeof(RenderBlock::MarginInfo) == sizeof(SameSizeAsMarginInfo), MarginInfo_should_stay_small);
 }
 
 static void removeBlockFromDescendantAndContainerMaps(RenderBlock* block, TrackedDescendantsMap*& descendantMap, TrackedContainerMap*& containerMap)
 {
-    if (OwnPtr<TrackedRendererListHashSet> descendantSet = descendantMap->take(block)) {
+    if (std::unique_ptr<TrackedRendererListHashSet> descendantSet = descendantMap->take(block)) {
         TrackedRendererListHashSet::iterator end = descendantSet->end();
         for (TrackedRendererListHashSet::iterator descendant = descendantSet->begin(); descendant != end; ++descendant) {
             TrackedContainerMap::iterator it = containerMap->find(*descendant);
@@ -229,113 +212,70 @@ static void removeBlockFromDescendantAndContainerMaps(RenderBlock* block, Tracke
 
 RenderBlock::~RenderBlock()
 {
-    if (m_floatingObjects)
-        deleteAllValues(m_floatingObjects->set());
-    
-    if (hasColumns())
-        gColumnInfoMap->take(this);
+    removeFromUpdateScrollInfoAfterLayoutTransaction();
 
+    if (gRareDataMap)
+        gRareDataMap->remove(this);
     if (gPercentHeightDescendantsMap)
         removeBlockFromDescendantAndContainerMaps(this, gPercentHeightDescendantsMap, gPercentHeightContainerMap);
     if (gPositionedDescendantsMap)
         removeBlockFromDescendantAndContainerMaps(this, gPositionedDescendantsMap, gPositionedContainerMap);
 }
 
-RenderBlock* RenderBlock::createAnonymous(Document* document)
-{
-    RenderBlock* renderer = new (document->renderArena()) RenderBlock(0);
-    renderer->setDocumentForAnonymous(document);
-    return renderer;
-}
-
 void RenderBlock::willBeDestroyed()
 {
-    // Mark as being destroyed to avoid trouble with merges in removeChild().
-    m_beingDestroyed = true;
-
-    if (!documentBeingDestroyed()) {
-        if (firstChild() && firstChild()->isRunIn())
-            moveRunInToOriginalPosition(firstChild());
-    }
-
-    // Make sure to destroy anonymous children first while they are still connected to the rest of the tree, so that they will
-    // properly dirty line boxes that they are removed from. Effects that do :before/:after only on hover could crash otherwise.
-    children()->destroyLeftoverChildren();
-
-    // Destroy our continuation before anything other than anonymous children.
-    // The reason we don't destroy it before anonymous children is that they may
-    // have continuations of their own that are anonymous children of our continuation.
-    RenderBoxModelObject* continuation = this->continuation();
-    if (continuation) {
-        continuation->destroy();
-        setContinuation(0);
-    }
-    
     if (!documentBeingDestroyed()) {
-        if (firstLineBox()) {
-            // We can't wait for RenderBox::destroy to clear the selection,
-            // because by then we will have nuked the line boxes.
-            // FIXME: The FrameSelection should be responsible for this when it
-            // is notified of DOM mutations.
-            if (isSelectionBorder())
-                view()->clearSelection();
-
-            // If we are an anonymous block, then our line boxes might have children
-            // that will outlast this block. In the non-anonymous block case those
-            // children will be destroyed by the time we return from this function.
-            if (isAnonymousBlock()) {
-                for (InlineFlowBox* box = firstLineBox(); box; box = box->nextLineBox()) {
-                    while (InlineBox* childBox = box->firstChild())
-                        childBox->remove();
-                }
-            }
-        } else if (parent())
-            parent()->dirtyLinesFromChangedChild(this);
+        if (parent())
+            parent()->dirtyLinesFromChangedChild(*this);
     }
 
-    m_lineBoxes.deleteLineBoxes(renderArena());
-
-    if (lineGridBox())
-        lineGridBox()->destroy(renderArena());
-
-    if (UNLIKELY(gDelayedUpdateScrollInfoSet != 0))
-        gDelayedUpdateScrollInfoSet->remove(this);
-
     RenderBox::willBeDestroyed();
 }
 
-void RenderBlock::styleWillChange(StyleDifference diff, const RenderStyle* newStyle)
+bool RenderBlock::hasRareData() const
+{
+    return gRareDataMap ? gRareDataMap->contains(this) : false;
+}
+
+void RenderBlock::removePositionedObjectsIfNeeded(const RenderStyle& oldStyle, const RenderStyle& newStyle)
 {
-    RenderStyle* oldStyle = style();
-    s_canPropagateFloatIntoSibling = oldStyle ? !isFloatingOrOutOfFlowPositioned() && !avoidsFloats() : false;
+    bool hadTransform = oldStyle.hasTransformRelatedProperty();
+    bool willHaveTransform = newStyle.hasTransformRelatedProperty();
+    if (oldStyle.position() == newStyle.position() && hadTransform == willHaveTransform)
+        return;
 
-    setReplaced(newStyle->isDisplayInlineType());
+    // We are no longer a containing block.
+    if (newStyle.position() == StaticPosition && !willHaveTransform) {
+        // Clear our positioned objects list. Our absolutely positioned descendants will be
+        // inserted into our containing block's positioned objects list during layout.
+        removePositionedObjects(nullptr, NewContainingBlock);
+        return;
+    }
     
-    if (oldStyle && parent() && diff == StyleDifferenceLayout && oldStyle->position() != newStyle->position()) {
-        if (newStyle->position() == StaticPosition)
-            // Clear our positioned objects list. Our absolutely positioned descendants will be
-            // inserted into our containing block's positioned objects list during layout.
-            removePositionedObjects(0, NewContainingBlock);
-        else if (oldStyle->position() == StaticPosition) {
-            // Remove our absolutely positioned descendants from their current containing block.
-            // They will be inserted into our positioned objects list during layout.
-            RenderObject* cb = parent();
-            while (cb && (cb->style()->position() == StaticPosition || (cb->isInline() && !cb->isReplaced())) && !cb->isRenderView()) {
-                if (cb->style()->position() == RelativePosition && cb->isInline() && !cb->isReplaced()) {
-                    cb = cb->containingBlock();
-                    break;
-                }
-                cb = cb->parent();
+    // We are a new containing block.
+    if (oldStyle.position() == StaticPosition && !hadTransform) {
+        // Remove our absolutely positioned descendants from their current containing block.
+        // They will be inserted into our positioned objects list during layout.
+        auto* containingBlock = parent();
+        while (containingBlock && !is<RenderView>(*containingBlock)
+            && (containingBlock->style().position() == StaticPosition || (containingBlock->isInline() && !containingBlock->isReplaced()))) {
+            if (containingBlock->style().position() == RelativePosition && containingBlock->isInline() && !containingBlock->isReplaced()) {
+                containingBlock = containingBlock->containingBlock();
+                break;
             }
-            
-            if (cb->isRenderBlock())
-                toRenderBlock(cb)->removePositionedObjects(this, NewContainingBlock);
+            containingBlock = containingBlock->parent();
         }
-
-        if (containsFloats() && !isFloating() && !isOutOfFlowPositioned() && newStyle->hasOutOfFlowPosition())
-            markAllDescendantsWithFloatsForLayout();
+        if (containingBlock && is<RenderBlock>(*containingBlock))
+            downcast<RenderBlock>(*containingBlock).removePositionedObjects(this, NewContainingBlock);
     }
+}
 
+void RenderBlock::styleWillChange(StyleDifference diff, const RenderStyle& newStyle)
+{
+    const RenderStyle* oldStyle = hasInitializedStyle() ? &style() : nullptr;
+    setReplaced(newStyle.isDisplayInlineType());
+    if (oldStyle)
+        removePositionedObjectsIfNeeded(*oldStyle, newStyle);
     RenderBox::styleWillChange(diff, newStyle);
 }
 
@@ -355,13 +295,19 @@ static bool borderOrPaddingLogicalWidthChanged(const RenderStyle* oldStyle, cons
 
 void RenderBlock::styleDidChange(StyleDifference diff, const RenderStyle* oldStyle)
 {
+    RenderStyle& newStyle = style();
+
+    bool hadTransform = hasTransform();
+    bool flowThreadContainingBlockInvalidated = false;
+    if (oldStyle && oldStyle->position() != newStyle.position()) {
+        invalidateFlowThreadContainingBlockIncludingDescendants();
+        flowThreadContainingBlockInvalidated = true;
+    }
+
     RenderBox::styleDidChange(diff, oldStyle);
-    
-    RenderStyle* newStyle = style();
-    
-#if ENABLE(CSS_SHAPES)
-    updateShapeInsideInfoAfterStyleChange(newStyle->resolvedShapeInside(), oldStyle ? oldStyle->resolvedShapeInside() : 0);
-#endif
+
+    if (hadTransform != hasTransform() && !flowThreadContainingBlockInvalidated)
+        invalidateFlowThreadContainingBlockIncludingDescendants();
 
     if (!isAnonymousBlock()) {
         // Ensure that all of our continuation blocks pick up the new style.
@@ -373,42 +319,11 @@ void RenderBlock::styleDidChange(StyleDifference diff, const RenderStyle* oldSty
         }
     }
 
-    propagateStyleToAnonymousChildren(true);    
-    m_lineHeight = -1;
-
-    // After our style changed, if we lose our ability to propagate floats into next sibling
-    // blocks, then we need to find the top most parent containing that overhanging float and
-    // then mark its descendants with floats for layout and clear all floats from its next
-    // sibling blocks that exist in our floating objects list. See bug 56299 and 62875.
-    bool canPropagateFloatIntoSibling = !isFloatingOrOutOfFlowPositioned() && !avoidsFloats();
-    if (diff == StyleDifferenceLayout && s_canPropagateFloatIntoSibling && !canPropagateFloatIntoSibling && hasOverhangingFloats()) {
-        RenderBlock* parentBlock = this;
-        const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-        FloatingObjectSetIterator end = floatingObjectSet.end();
-
-        for (RenderObject* curr = parent(); curr && !curr->isRenderView(); curr = curr->parent()) {
-            if (curr->isRenderBlock()) {
-                RenderBlock* currBlock = toRenderBlock(curr);
-
-                if (currBlock->hasOverhangingFloats()) {
-                    for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-                        RenderBox* renderer = (*it)->renderer();
-                        if (currBlock->hasOverhangingFloat(renderer)) {
-                            parentBlock = currBlock;
-                            break;
-                        }
-                    }
-                }
-            }
-        }
-              
-        parentBlock->markAllDescendantsWithFloatsForLayout();
-        parentBlock->markSiblingsWithFloatsForLayout();
-    }
-    
+    propagateStyleToAnonymousChildren(PropagateToBlockChildrenOnly);
+
     // It's possible for our border/padding to change, but for the overall logical width of the block to
     // end up being the same. We keep track of this change so in layoutBlock, we can know to set relayoutChildren=true.
-    m_hasBorderOrPaddingLogicalWidthChanged = oldStyle && diff == StyleDifferenceLayout && needsLayout() && borderOrPaddingLogicalWidthChanged(oldStyle, newStyle);
+    setHasBorderOrPaddingLogicalWidthChanged(oldStyle && diff == StyleDifferenceLayout && needsLayout() && borderOrPaddingLogicalWidthChanged(oldStyle, &newStyle));
 }
 
 RenderBlock* RenderBlock::continuationBefore(RenderObject* beforeChild)
@@ -416,19 +331,17 @@ RenderBlock* RenderBlock::continuationBefore(RenderObject* beforeChild)
     if (beforeChild && beforeChild->parent() == this)
         return this;
 
-    RenderBlock* curr = toRenderBlock(continuation());
     RenderBlock* nextToLast = this;
     RenderBlock* last = this;
-    while (curr) {
-        if (beforeChild && beforeChild->parent() == curr) {
-            if (curr->firstChild() == beforeChild)
+    for (auto* current = downcast<RenderBlock>(continuation()); current; current = downcast<RenderBlock>(current->continuation())) {
+        if (beforeChild && beforeChild->parent() == current) {
+            if (current->firstChild() == beforeChild)
                 return last;
-            return curr;
+            return current;
         }
 
         nextToLast = last;
-        last = curr;
-        curr = toRenderBlock(curr->continuation());
+        last = current;
     }
 
     if (!beforeChild && !last->firstChild())
@@ -439,14 +352,14 @@ RenderBlock* RenderBlock::continuationBefore(RenderObject* beforeChild)
 void RenderBlock::addChildToContinuation(RenderObject* newChild, RenderObject* beforeChild)
 {
     RenderBlock* flow = continuationBefore(beforeChild);
-    ASSERT(!beforeChild || beforeChild->parent()->isAnonymousColumnSpanBlock() || beforeChild->parent()->isRenderBlock());
-    RenderBoxModelObject* beforeChildParent = 0;
+    ASSERT(!beforeChild || is<RenderBlock>(*beforeChild->parent()));
+    RenderBoxModelObject* beforeChildParent = nullptr;
     if (beforeChild)
-        beforeChildParent = toRenderBoxModelObject(beforeChild->parent());
+        beforeChildParent = downcast<RenderBoxModelObject>(beforeChild->parent());
     else {
-        RenderBoxModelObject* cont = flow->continuation();
-        if (cont)
-            beforeChildParent = cont;
+        RenderBoxModelObject* continuation = flow->continuation();
+        if (continuation)
+            beforeChildParent = continuation;
         else
             beforeChildParent = flow;
     }
@@ -456,11 +369,9 @@ void RenderBlock::addChildToContinuation(RenderObject* newChild, RenderObject* b
         return;
     }
 
-    // A continuation always consists of two potential candidates: a block or an anonymous
-    // column span box holding column span children.
-    bool childIsNormal = newChild->isInline() || !newChild->style()->columnSpan();
-    bool bcpIsNormal = beforeChildParent->isInline() || !beforeChildParent->style()->columnSpan();
-    bool flowIsNormal = flow->isInline() || !flow->style()->columnSpan();
+    bool childIsNormal = newChild->isInline() || !newChild->style().columnSpan();
+    bool bcpIsNormal = beforeChildParent->isInline() || !beforeChildParent->style().columnSpan();
+    bool flowIsNormal = flow->isInline() || !flow->style().columnSpan();
 
     if (flow == beforeChildParent) {
         flow->addChildIgnoringContinuation(newChild, beforeChild);
@@ -480,107 +391,16 @@ void RenderBlock::addChildToContinuation(RenderObject* newChild, RenderObject* b
     beforeChildParent->addChildIgnoringContinuation(newChild, beforeChild);
 }
 
-
-void RenderBlock::addChildToAnonymousColumnBlocks(RenderObject* newChild, RenderObject* beforeChild)
-{
-    ASSERT(!continuation()); // We don't yet support column spans that aren't immediate children of the multi-column block.
-        
-    // The goal is to locate a suitable box in which to place our child.
-    RenderBlock* beforeChildParent = 0;
-    if (beforeChild) {
-        RenderObject* curr = beforeChild;
-        while (curr && curr->parent() != this)
-            curr = curr->parent();
-        beforeChildParent = toRenderBlock(curr);
-        ASSERT(beforeChildParent);
-        ASSERT(beforeChildParent->isAnonymousColumnsBlock() || beforeChildParent->isAnonymousColumnSpanBlock());
-    } else
-        beforeChildParent = toRenderBlock(lastChild());
-
-    // If the new child is floating or positioned it can just go in that block.
-    if (newChild->isFloatingOrOutOfFlowPositioned()) {
-        beforeChildParent->addChildIgnoringAnonymousColumnBlocks(newChild, beforeChild);
-        return;
-    }
-
-    // See if the child can be placed in the box.
-    bool newChildHasColumnSpan = newChild->style()->columnSpan() && !newChild->isInline();
-    bool beforeChildParentHoldsColumnSpans = beforeChildParent->isAnonymousColumnSpanBlock();
-
-    if (newChildHasColumnSpan == beforeChildParentHoldsColumnSpans) {
-        beforeChildParent->addChildIgnoringAnonymousColumnBlocks(newChild, beforeChild);
-        return;
-    }
-
-    if (!beforeChild) {
-        // Create a new block of the correct type.
-        RenderBlock* newBox = newChildHasColumnSpan ? createAnonymousColumnSpanBlock() : createAnonymousColumnsBlock();
-        children()->appendChildNode(this, newBox);
-        newBox->addChildIgnoringAnonymousColumnBlocks(newChild, 0);
-        return;
-    }
-
-    RenderObject* immediateChild = beforeChild;
-    bool isPreviousBlockViable = true;
-    while (immediateChild->parent() != this) {
-        if (isPreviousBlockViable)
-            isPreviousBlockViable = !immediateChild->previousSibling();
-        immediateChild = immediateChild->parent();
-    }
-    if (isPreviousBlockViable && immediateChild->previousSibling()) {
-        toRenderBlock(immediateChild->previousSibling())->addChildIgnoringAnonymousColumnBlocks(newChild, 0); // Treat like an append.
-        return;
-    }
-        
-    // Split our anonymous blocks.
-    RenderObject* newBeforeChild = splitAnonymousBoxesAroundChild(beforeChild);
-
-    
-    // Create a new anonymous box of the appropriate type.
-    RenderBlock* newBox = newChildHasColumnSpan ? createAnonymousColumnSpanBlock() : createAnonymousColumnsBlock();
-    children()->insertChildNode(this, newBox, newBeforeChild);
-    newBox->addChildIgnoringAnonymousColumnBlocks(newChild, 0);
-    return;
-}
-
-RenderBlock* RenderBlock::containingColumnsBlock(bool allowAnonymousColumnBlock)
-{
-    RenderBlock* firstChildIgnoringAnonymousWrappers = 0;
-    for (RenderObject* curr = this; curr; curr = curr->parent()) {
-        if (!curr->isRenderBlock() || curr->isFloatingOrOutOfFlowPositioned() || curr->isTableCell() || curr->isRoot() || curr->isRenderView() || curr->hasOverflowClip()
-            || curr->isInlineBlockOrInlineTable())
-            return 0;
-
-        // FIXME: Tables, RenderButtons, and RenderListItems all do special management
-        // of their children that breaks when the flow is split through them. Disabling
-        // multi-column for them to avoid this problem.
-        if (curr->isTable() || curr->isRenderButton() || curr->isListItem())
-            return 0;
-        
-        RenderBlock* currBlock = toRenderBlock(curr);
-        if (!currBlock->createsAnonymousWrapper())
-            firstChildIgnoringAnonymousWrappers = currBlock;
-
-        if (currBlock->style()->specifiesColumns() && (allowAnonymousColumnBlock || !currBlock->isAnonymousColumnsBlock()))
-            return firstChildIgnoringAnonymousWrappers;
-            
-        if (currBlock->isAnonymousColumnSpanBlock())
-            return 0;
-    }
-    return 0;
-}
-
-RenderBlock* RenderBlock::clone() const
+RenderPtr<RenderBlock> RenderBlock::clone() const
 {
-    RenderBlock* cloneBlock;
+    RenderPtr<RenderBlock> cloneBlock;
     if (isAnonymousBlock()) {
-        cloneBlock = createAnonymousBlock();
+        cloneBlock = RenderPtr<RenderBlock>(createAnonymousBlock());
         cloneBlock->setChildrenInline(childrenInline());
-    }
-    else {
-        RenderObject* cloneRenderer = toElement(node())->createRenderer(renderArena(), style());
-        cloneBlock = toRenderBlock(cloneRenderer);
-        cloneBlock->setStyle(style());
+    } else {
+        RenderTreePosition insertionPosition(*parent());
+        cloneBlock = static_pointer_cast<RenderBlock>(element()->createElementRenderer(style(), insertionPosition));
+        cloneBlock->initializeStyle();
 
         // This takes care of setting the right value of childrenInline in case
         // generated content is added to cloneBlock and 'this' does not have
@@ -591,220 +411,18 @@ RenderBlock* RenderBlock::clone() const
     return cloneBlock;
 }
 
-void RenderBlock::splitBlocks(RenderBlock* fromBlock, RenderBlock* toBlock,
-                              RenderBlock* middleBlock,
-                              RenderObject* beforeChild, RenderBoxModelObject* oldCont)
-{
-    // Create a clone of this inline.
-    RenderBlock* cloneBlock = clone();
-    if (!isAnonymousBlock())
-        cloneBlock->setContinuation(oldCont);
-
-    if (!beforeChild && isAfterContent(lastChild()))
-        beforeChild = lastChild();
-
-    // If we are moving inline children from |this| to cloneBlock, then we need
-    // to clear our line box tree.
-    if (beforeChild && childrenInline())
-        deleteLineBoxTree();
-
-    // Now take all of the children from beforeChild to the end and remove
-    // them from |this| and place them in the clone.
-    moveChildrenTo(cloneBlock, beforeChild, 0, true);
-    
-    // Hook |clone| up as the continuation of the middle block.
-    if (!cloneBlock->isAnonymousBlock())
-        middleBlock->setContinuation(cloneBlock);
-
-    // We have been reparented and are now under the fromBlock.  We need
-    // to walk up our block parent chain until we hit the containing anonymous columns block.
-    // Once we hit the anonymous columns block we're done.
-    RenderBoxModelObject* curr = toRenderBoxModelObject(parent());
-    RenderBoxModelObject* currChild = this;
-    RenderObject* currChildNextSibling = currChild->nextSibling();
-
-    while (curr && curr != fromBlock) {
-        ASSERT_WITH_SECURITY_IMPLICATION(curr->isRenderBlock());
-        
-        RenderBlock* blockCurr = toRenderBlock(curr);
-        
-        // Create a new clone.
-        RenderBlock* cloneChild = cloneBlock;
-        cloneBlock = blockCurr->clone();
-
-        // Insert our child clone as the first child.
-        cloneBlock->addChildIgnoringContinuation(cloneChild, 0);
-
-        // Hook the clone up as a continuation of |curr|.  Note we do encounter
-        // anonymous blocks possibly as we walk up the block chain.  When we split an
-        // anonymous block, there's no need to do any continuation hookup, since we haven't
-        // actually split a real element.
-        if (!blockCurr->isAnonymousBlock()) {
-            oldCont = blockCurr->continuation();
-            blockCurr->setContinuation(cloneBlock);
-            cloneBlock->setContinuation(oldCont);
-        }
-
-        // Now we need to take all of the children starting from the first child
-        // *after* currChild and append them all to the clone.
-        blockCurr->moveChildrenTo(cloneBlock, currChildNextSibling, 0, true);
-
-        // Keep walking up the chain.
-        currChild = curr;
-        currChildNextSibling = currChild->nextSibling();
-        curr = toRenderBoxModelObject(curr->parent());
-    }
-
-    // Now we are at the columns block level. We need to put the clone into the toBlock.
-    toBlock->children()->appendChildNode(toBlock, cloneBlock);
-
-    // Now take all the children after currChild and remove them from the fromBlock
-    // and put them in the toBlock.
-    fromBlock->moveChildrenTo(toBlock, currChildNextSibling, 0, true);
-}
-
-void RenderBlock::splitFlow(RenderObject* beforeChild, RenderBlock* newBlockBox,
-                            RenderObject* newChild, RenderBoxModelObject* oldCont)
-{
-    RenderBlock* pre = 0;
-    RenderBlock* block = containingColumnsBlock();
-    
-    // Delete our line boxes before we do the inline split into continuations.
-    block->deleteLineBoxTree();
-    
-    bool madeNewBeforeBlock = false;
-    if (block->isAnonymousColumnsBlock()) {
-        // We can reuse this block and make it the preBlock of the next continuation.
-        pre = block;
-        pre->removePositionedObjects(0);
-        pre->removeFloatingObjects();
-        block = toRenderBlock(block->parent());
-    } else {
-        // No anonymous block available for use.  Make one.
-        pre = block->createAnonymousColumnsBlock();
-        pre->setChildrenInline(false);
-        madeNewBeforeBlock = true;
-    }
-
-    RenderBlock* post = block->createAnonymousColumnsBlock();
-    post->setChildrenInline(false);
-
-    RenderObject* boxFirst = madeNewBeforeBlock ? block->firstChild() : pre->nextSibling();
-    if (madeNewBeforeBlock)
-        block->children()->insertChildNode(block, pre, boxFirst);
-    block->children()->insertChildNode(block, newBlockBox, boxFirst);
-    block->children()->insertChildNode(block, post, boxFirst);
-    block->setChildrenInline(false);
-    
-    if (madeNewBeforeBlock)
-        block->moveChildrenTo(pre, boxFirst, 0, true);
-
-    splitBlocks(pre, post, newBlockBox, beforeChild, oldCont);
-
-    // We already know the newBlockBox isn't going to contain inline kids, so avoid wasting
-    // time in makeChildrenNonInline by just setting this explicitly up front.
-    newBlockBox->setChildrenInline(false);
-
-    // We delayed adding the newChild until now so that the |newBlockBox| would be fully
-    // connected, thus allowing newChild access to a renderArena should it need
-    // to wrap itself in additional boxes (e.g., table construction).
-    newBlockBox->addChild(newChild);
-
-    // Always just do a full layout in order to ensure that line boxes (especially wrappers for images)
-    // get deleted properly.  Because objects moves from the pre block into the post block, we want to
-    // make new line boxes instead of leaving the old line boxes around.
-    pre->setNeedsLayoutAndPrefWidthsRecalc();
-    block->setNeedsLayoutAndPrefWidthsRecalc();
-    post->setNeedsLayoutAndPrefWidthsRecalc();
-}
-
-void RenderBlock::makeChildrenAnonymousColumnBlocks(RenderObject* beforeChild, RenderBlock* newBlockBox, RenderObject* newChild)
+void RenderBlock::addChild(RenderObject* newChild, RenderObject* beforeChild)
 {
-    RenderBlock* pre = 0;
-    RenderBlock* post = 0;
-    RenderBlock* block = this; // Eventually block will not just be |this|, but will also be a block nested inside |this|.  Assign to a variable
-                               // so that we don't have to patch all of the rest of the code later on.
-    
-    // Delete the block's line boxes before we do the split.
-    block->deleteLineBoxTree();
-
-    if (beforeChild && beforeChild->parent() != this)
-        beforeChild = splitAnonymousBoxesAroundChild(beforeChild);
-
-    if (beforeChild != firstChild()) {
-        pre = block->createAnonymousColumnsBlock();
-        pre->setChildrenInline(block->childrenInline());
-    }
-
-    if (beforeChild) {
-        post = block->createAnonymousColumnsBlock();
-        post->setChildrenInline(block->childrenInline());
-    }
-
-    RenderObject* boxFirst = block->firstChild();
-    if (pre)
-        block->children()->insertChildNode(block, pre, boxFirst);
-    block->children()->insertChildNode(block, newBlockBox, boxFirst);
-    if (post)
-        block->children()->insertChildNode(block, post, boxFirst);
-    block->setChildrenInline(false);
-    
-    // The pre/post blocks always have layers, so we know to always do a full insert/remove (so we pass true as the last argument).
-    block->moveChildrenTo(pre, boxFirst, beforeChild, true);
-    block->moveChildrenTo(post, beforeChild, 0, true);
-
-    // We already know the newBlockBox isn't going to contain inline kids, so avoid wasting
-    // time in makeChildrenNonInline by just setting this explicitly up front.
-    newBlockBox->setChildrenInline(false);
-
-    // We delayed adding the newChild until now so that the |newBlockBox| would be fully
-    // connected, thus allowing newChild access to a renderArena should it need
-    // to wrap itself in additional boxes (e.g., table construction).
-    newBlockBox->addChild(newChild);
-
-    // Always just do a full layout in order to ensure that line boxes (especially wrappers for images)
-    // get deleted properly.  Because objects moved from the pre block into the post block, we want to
-    // make new line boxes instead of leaving the old line boxes around.
-    if (pre)
-        pre->setNeedsLayoutAndPrefWidthsRecalc();
-    block->setNeedsLayoutAndPrefWidthsRecalc();
-    if (post)
-        post->setNeedsLayoutAndPrefWidthsRecalc();
-}
-
-RenderBlock* RenderBlock::columnsBlockForSpanningElement(RenderObject* newChild)
-{
-    // FIXME: This function is the gateway for the addition of column-span support.  It will
-    // be added to in three stages:
-    // (1) Immediate children of a multi-column block can span.
-    // (2) Nested block-level children with only block-level ancestors between them and the multi-column block can span.
-    // (3) Nested children with block or inline ancestors between them and the multi-column block can span (this is when we
-    // cross the streams and have to cope with both types of continuations mixed together).
-    // This function currently supports (1) and (2).
-    RenderBlock* columnsBlockAncestor = 0;
-    if (!newChild->isText() && newChild->style()->columnSpan() && !newChild->isBeforeOrAfterContent()
-        && !newChild->isFloatingOrOutOfFlowPositioned() && !newChild->isInline() && !isAnonymousColumnSpanBlock()) {
-        columnsBlockAncestor = containingColumnsBlock(false);
-        if (columnsBlockAncestor) {
-            // Make sure that none of the parent ancestors have a continuation.
-            // If yes, we do not want split the block into continuations.
-            RenderObject* curr = this;
-            while (curr && curr != columnsBlockAncestor) {
-                if (curr->isRenderBlock() && toRenderBlock(curr)->continuation()) {
-                    columnsBlockAncestor = 0;
-                    break;
-                }
-                curr = curr->parent();
-            }
-        }
-    }
-    return columnsBlockAncestor;
+    if (continuation() && !isAnonymousBlock())
+        addChildToContinuation(newChild, beforeChild);
+    else
+        addChildIgnoringContinuation(newChild, beforeChild);
 }
 
-void RenderBlock::addChildIgnoringAnonymousColumnBlocks(RenderObject* newChild, RenderObject* beforeChild)
+void RenderBlock::addChildIgnoringContinuation(RenderObject* newChild, RenderObject* beforeChild)
 {
     if (beforeChild && beforeChild->parent() != this) {
-        RenderObject* beforeChildContainer = beforeChild->parent();
+        RenderElement* beforeChildContainer = beforeChild->parent();
         while (beforeChildContainer->parent() != this)
             beforeChildContainer = beforeChildContainer->parent();
         ASSERT(beforeChildContainer);
@@ -812,7 +430,7 @@ void RenderBlock::addChildIgnoringAnonymousColumnBlocks(RenderObject* newChild,
         if (beforeChildContainer->isAnonymous()) {
             // If the requested beforeChild is not one of our children, then this is because
             // there is an anonymous container within this object that contains the beforeChild.
-            RenderObject* beforeChildAnonymousContainer = beforeChildContainer;
+            RenderElement* beforeChildAnonymousContainer = beforeChildContainer;
             if (beforeChildAnonymousContainer->isAnonymousBlock()
 #if ENABLE(FULLSCREEN_API)
                 // Full screen renderers and full screen placeholders act as anonymous blocks, not tables:
@@ -843,47 +461,6 @@ void RenderBlock::addChildIgnoringAnonymousColumnBlocks(RenderObject* newChild,
                 // safe fallback to use the topmost beforeChild container.
                 beforeChild = beforeChildContainer;
             }
-        } else {
-            // We will reach here when beforeChild is a run-in element.
-            // If run-in element precedes a block-level element, it becomes the
-            // the first inline child of that block level element. The insertion
-            // point will be before that block-level element.
-            ASSERT(beforeChild->isRunIn());
-            beforeChild = beforeChildContainer;
-        }
-    }
-
-    // Nothing goes before the intruded run-in.
-    if (beforeChild && beforeChild->isRunIn() && runInIsPlacedIntoSiblingBlock(beforeChild))
-        beforeChild = beforeChild->nextSibling();
-
-    // Check for a spanning element in columns.
-    if (gColumnFlowSplitEnabled) {
-        RenderBlock* columnsBlockAncestor = columnsBlockForSpanningElement(newChild);
-        if (columnsBlockAncestor) {
-            TemporaryChange<bool> columnFlowSplitEnabled(gColumnFlowSplitEnabled, false);
-            // We are placing a column-span element inside a block.
-            RenderBlock* newBox = createAnonymousColumnSpanBlock();
-        
-            if (columnsBlockAncestor != this && !isRenderFlowThread()) {
-                // We are nested inside a multi-column element and are being split by the span. We have to break up
-                // our block into continuations.
-                RenderBoxModelObject* oldContinuation = continuation();
-
-                // When we split an anonymous block, there's no need to do any continuation hookup,
-                // since we haven't actually split a real element.
-                if (!isAnonymousBlock())
-                    setContinuation(newBox);
-
-                splitFlow(beforeChild, newBox, newChild, oldContinuation);
-                return;
-            }
-
-            // We have to perform a split of this block's children. This involves creating an anonymous block box to hold
-            // the column-spanning |newChild|. We take all of the children from before |newChild| and put them into
-            // one anonymous columns block, and all of the children after |newChild| go into another anonymous block.
-            makeChildrenAnonymousColumnBlocks(beforeChild, newBox, newChild);
-            return;
         }
     }
 
@@ -909,7 +486,7 @@ void RenderBlock::addChildIgnoringAnonymousColumnBlocks(RenderObject* newChild,
         RenderObject* afterChild = beforeChild ? beforeChild->previousSibling() : lastChild();
 
         if (afterChild && afterChild->isAnonymousBlock()) {
-            afterChild->addChild(newChild);
+            downcast<RenderBlock>(*afterChild).addChild(newChild);
             return;
         }
 
@@ -922,32 +499,15 @@ void RenderBlock::addChildIgnoringAnonymousColumnBlocks(RenderObject* newChild,
         }
     }
 
+    invalidateLineLayoutPath();
+
     RenderBox::addChild(newChild, beforeChild);
  
-    // Handle placement of run-ins.
-    placeRunInIfNeeded(newChild);
-
-    if (madeBoxesNonInline && parent() && isAnonymousBlock() && parent()->isRenderBlock())
-        toRenderBlock(parent())->removeLeftoverAnonymousBlock(this);
+    if (madeBoxesNonInline && is<RenderBlock>(parent()) && isAnonymousBlock())
+        downcast<RenderBlock>(*parent()).removeLeftoverAnonymousBlock(this);
     // this object may be dead here
 }
 
-void RenderBlock::addChild(RenderObject* newChild, RenderObject* beforeChild)
-{
-    if (continuation() && !isAnonymousBlock())
-        addChildToContinuation(newChild, beforeChild);
-    else
-        addChildIgnoringContinuation(newChild, beforeChild);
-}
-
-void RenderBlock::addChildIgnoringContinuation(RenderObject* newChild, RenderObject* beforeChild)
-{
-    if (!isAnonymousBlock() && firstChild() && (firstChild()->isAnonymousColumnsBlock() || firstChild()->isAnonymousColumnSpanBlock()))
-        addChildToAnonymousColumnBlocks(newChild, beforeChild);
-    else
-        addChildIgnoringAnonymousColumnBlocks(newChild, beforeChild);
-}
-
 static void getInlineRun(RenderObject* start, RenderObject* boundary,
                          RenderObject*& inlineRunStart,
                          RenderObject*& inlineRunEnd)
@@ -988,42 +548,13 @@ static void getInlineRun(RenderObject* start, RenderObject* boundary,
     } while (!sawInline);
 }
 
-void RenderBlock::deleteLineBoxTree()
+void RenderBlock::deleteLines()
 {
-    if (containsFloats()) {
-        // Clear references to originating lines, since the lines are being deleted
-        const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-        FloatingObjectSetIterator end = floatingObjectSet.end();
-        for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-            ASSERT(!((*it)->m_originatingLine) || (*it)->m_originatingLine->renderer() == this);
-            (*it)->m_originatingLine = 0;
-        }
-    }
-    m_lineBoxes.deleteLineBoxTree(renderArena());
-
-    if (AXObjectCache* cache = document()->existingAXObjectCache())
+    if (AXObjectCache* cache = document().existingAXObjectCache())
         cache->recomputeIsIgnored(this);
 }
 
-RootInlineBox* RenderBlock::createRootInlineBox()
-{
-    return new (renderArena()) RootInlineBox(this);
-}
-
-RootInlineBox* RenderBlock::createAndAppendRootInlineBox()
-{
-    RootInlineBox* rootBox = createRootInlineBox();
-    m_lineBoxes.appendLineBox(rootBox);
-
-    if (UNLIKELY(AXObjectCache::accessibilityEnabled()) && m_lineBoxes.firstLineBox() == rootBox) {
-        if (AXObjectCache* cache = document()->existingAXObjectCache())
-            cache->recomputeIsIgnored(this);
-    }
-
-    return rootBox;
-}
-
-void RenderBlock::makeChildrenNonInline(RenderObject *insertionPoint)
+void RenderBlock::makeChildrenNonInline(RenderObject* insertionPoint)
 {    
     // makeChildrenNonInline takes a block whose children are *all* inline and it
     // makes sure that inline children are coalesced under anonymous
@@ -1037,21 +568,15 @@ void RenderBlock::makeChildrenNonInline(RenderObject *insertionPoint)
 
     setChildrenInline(false);
 
-    RenderObject *child = firstChild();
+    RenderObject* child = firstChild();
     if (!child)
         return;
 
-    deleteLineBoxTree();
-
-    // Since we are going to have block children, we have to move
-    // back the run-in to its original place.
-    if (child->isRunIn()) {
-        moveRunInToOriginalPosition(child);
-        child = firstChild();
-    }
+    deleteLines();
 
     while (child) {
-        RenderObject *inlineRunStart, *inlineRunEnd;
+        RenderObject* inlineRunStart;
+        RenderObject* inlineRunEnd;
         getInlineRun(child, insertionPoint, inlineRunStart, inlineRunEnd);
 
         if (!inlineRunStart)
@@ -1060,12 +585,12 @@ void RenderBlock::makeChildrenNonInline(RenderObject *insertionPoint)
         child = inlineRunEnd->nextSibling();
 
         RenderBlock* block = createAnonymousBlock();
-        children()->insertChildNode(this, block, inlineRunStart);
+        insertChildInternal(block, inlineRunStart, NotifyChildren);
         moveChildrenTo(block, inlineRunStart, child);
     }
 
 #ifndef NDEBUG
-    for (RenderObject *c = firstChild(); c; c = c->nextSibling())
+    for (RenderObject* c = firstChild(); c; c = c->nextSibling())
         ASSERT(!c->isInline());
 #endif
 
@@ -1077,11 +602,11 @@ void RenderBlock::removeLeftoverAnonymousBlock(RenderBlock* child)
     ASSERT(child->isAnonymousBlock());
     ASSERT(!child->childrenInline());
     
-    if (child->continuation() || (child->firstChild() && (child->isAnonymousColumnSpanBlock() || child->isAnonymousColumnsBlock())))
+    if (child->continuation())
         return;
     
-    RenderObject* firstAnChild = child->m_children.firstChild();
-    RenderObject* lastAnChild = child->m_children.lastChild();
+    RenderObject* firstAnChild = child->firstChild();
+    RenderObject* lastAnChild = child->lastChild();
     if (firstAnChild) {
         RenderObject* o = firstAnChild;
         while (o) {
@@ -1095,15 +620,15 @@ void RenderBlock::removeLeftoverAnonymousBlock(RenderBlock* child)
         if (child->nextSibling())
             child->nextSibling()->setPreviousSibling(lastAnChild);
             
-        if (child == m_children.firstChild())
-            m_children.setFirstChild(firstAnChild);
-        if (child == m_children.lastChild())
-            m_children.setLastChild(lastAnChild);
+        if (child == firstChild())
+            setFirstChild(firstAnChild);
+        if (child == lastChild())
+            setLastChild(lastAnChild);
     } else {
-        if (child == m_children.firstChild())
-            m_children.setFirstChild(child->nextSibling());
-        if (child == m_children.lastChild())
-            m_children.setLastChild(child->previousSibling());
+        if (child == firstChild())
+            setFirstChild(child->nextSibling());
+        if (child == lastChild())
+            setLastChild(child->previousSibling());
 
         if (child->previousSibling())
             child->previousSibling()->setNextSibling(child->nextSibling());
@@ -1111,7 +636,7 @@ void RenderBlock::removeLeftoverAnonymousBlock(RenderBlock* child)
             child->nextSibling()->setPreviousSibling(child->previousSibling());
     }
 
-    child->children()->setFirstChild(0);
+    child->setFirstChild(0);
     child->m_next = 0;
 
     // Remove all the information in the flow thread associated with the leftover anonymous block.
@@ -1124,90 +649,53 @@ void RenderBlock::removeLeftoverAnonymousBlock(RenderBlock* child)
     child->destroy();
 }
 
-static bool canMergeContiguousAnonymousBlocks(RenderObject* oldChild, RenderObject* prev, RenderObject* next)
+static bool canDropAnonymousBlock(const RenderBlock& anonymousBlock)
 {
-    if (oldChild->documentBeingDestroyed() || oldChild->isInline() || oldChild->virtualContinuation())
-        return false;
-
-    if ((prev && (!prev->isAnonymousBlock() || toRenderBlock(prev)->continuation() || toRenderBlock(prev)->beingDestroyed()))
-        || (next && (!next->isAnonymousBlock() || toRenderBlock(next)->continuation() || toRenderBlock(next)->beingDestroyed())))
+    if (anonymousBlock.beingDestroyed() || anonymousBlock.continuation())
         return false;
-
-    // FIXME: This check isn't required when inline run-ins can't be split into continuations.
-    if (prev && prev->firstChild() && prev->firstChild()->isInline() && prev->firstChild()->isRunIn())
+    if (anonymousBlock.isRubyRun() || anonymousBlock.isRubyBase())
         return false;
+    return true;
+}
 
-    if ((prev && (prev->isRubyRun() || prev->isRubyBase()))
-        || (next && (next->isRubyRun() || next->isRubyBase())))
+static bool canMergeContiguousAnonymousBlocks(RenderObject& oldChild, RenderObject* previous, RenderObject* next)
+{
+    if (oldChild.documentBeingDestroyed() || oldChild.isInline() || oldChild.virtualContinuation())
         return false;
 
-    if (!prev || !next)
-        return true;
-
-    // Make sure the types of the anonymous blocks match up.
-    return prev->isAnonymousColumnsBlock() == next->isAnonymousColumnsBlock()
-           && prev->isAnonymousColumnSpanBlock() == next->isAnonymousColumnSpanBlock();
+    if (previous) {
+        if (!previous->isAnonymousBlock())
+            return false;
+        RenderBlock& previousAnonymousBlock = downcast<RenderBlock>(*previous);
+        if (!canDropAnonymousBlock(previousAnonymousBlock))
+            return false;
+    }
+    if (next) {
+        if (!next->isAnonymousBlock())
+            return false;
+        RenderBlock& nextAnonymousBlock = downcast<RenderBlock>(*next);
+        if (!canDropAnonymousBlock(nextAnonymousBlock))
+            return false;
+    }
+    return true;
 }
 
-void RenderBlock::collapseAnonymousBoxChild(RenderBlock* parent, RenderObject* child)
+void RenderBlock::dropAnonymousBoxChild(RenderBlock& parent, RenderBlock& child)
 {
-    parent->setNeedsLayoutAndPrefWidthsRecalc();
-    parent->setChildrenInline(child->childrenInline());
-    RenderObject* nextSibling = child->nextSibling();
+    parent.setNeedsLayoutAndPrefWidthsRecalc();
+    parent.setChildrenInline(child.childrenInline());
+    if (auto* childFlowThread = child.flowThreadContainingBlock())
+        childFlowThread->removeFlowChildInfo(&child);
 
-    RenderFlowThread* childFlowThread = child->flowThreadContainingBlock();
-    CurrentRenderFlowThreadMaintainer flowThreadMaintainer(childFlowThread);
-    
-    RenderBlock* anonBlock = toRenderBlock(parent->children()->removeChildNode(parent, child, child->hasLayer()));
-    anonBlock->moveAllChildrenTo(parent, nextSibling, child->hasLayer());
+    RenderObject* nextSibling = child.nextSibling();
+    parent.removeChildInternal(child, child.hasLayer() ? NotifyChildren : DontNotifyChildren);
+    child.moveAllChildrenTo(&parent, nextSibling, child.hasLayer());
     // Delete the now-empty block's lines and nuke it.
-    anonBlock->deleteLineBoxTree();
-    if (childFlowThread && childFlowThread->isRenderNamedFlowThread())
-        toRenderNamedFlowThread(childFlowThread)->removeFlowChildInfo(anonBlock);
-    anonBlock->destroy();
-}
-
-void RenderBlock::moveAllChildrenIncludingFloatsTo(RenderBlock* toBlock, bool fullRemoveInsert)
-{
-    moveAllChildrenTo(toBlock, fullRemoveInsert);
-
-    // When a portion of the render tree is being detached, anonymous blocks
-    // will be combined as their children are deleted. In this process, the
-    // anonymous block later in the tree is merged into the one preceeding it.
-    // It can happen that the later block (this) contains floats that the
-    // previous block (toBlock) did not contain, and thus are not in the
-    // floating objects list for toBlock. This can result in toBlock containing
-    // floats that are not in it's floating objects list, but are in the
-    // floating objects lists of siblings and parents. This can cause problems
-    // when the float itself is deleted, since the deletion code assumes that
-    // if a float is not in it's containing block's floating objects list, it
-    // isn't in any floating objects list. In order to preserve this condition
-    // (removing it has serious performance implications), we need to copy the
-    // floating objects from the old block (this) to the new block (toBlock).
-    // The float's metrics will likely all be wrong, but since toBlock is
-    // already marked for layout, this will get fixed before anything gets
-    // displayed.
-    // See bug https://bugs.webkit.org/show_bug.cgi?id=115566
-    if (m_floatingObjects) {
-        if (!toBlock->m_floatingObjects)
-            toBlock->createFloatingObjects();
-
-        const FloatingObjectSet& fromFloatingObjectSet = m_floatingObjects->set();
-        FloatingObjectSetIterator end = fromFloatingObjectSet.end();
-
-        for (FloatingObjectSetIterator it = fromFloatingObjectSet.begin(); it != end; ++it) {
-            FloatingObject* floatingObject = *it;
-
-            // Don't insert the object again if it's already in the list
-            if (toBlock->containsFloat(floatingObject->renderer()))
-                continue;
-
-            toBlock->m_floatingObjects->add(floatingObject->clone());
-        }
-    }
+    child.deleteLines();
+    child.destroy();
 }
 
-void RenderBlock::removeChild(RenderObject* oldChild)
+void RenderBlock::removeChild(RenderObject& oldChild)
 {
     // No need to waste time in merging or removing empty anonymous blocks.
     // We can just bail out if our document is getting destroyed.
@@ -1216,111 +704,128 @@ void RenderBlock::removeChild(RenderObject* oldChild)
         return;
     }
 
-    // This protects against column split flows when anonymous blocks are getting merged.
-    TemporaryChange<bool> columnFlowSplitEnabled(gColumnFlowSplitEnabled, false);
-
-    // If this child is a block, and if our previous and next siblings are
-    // both anonymous blocks with inline content, then we can go ahead and
-    // fold the inline content back together.
-    RenderObject* prev = oldChild->previousSibling();
-    RenderObject* next = oldChild->nextSibling();
+    // If this child is a block, and if our previous and next siblings are both anonymous blocks
+    // with inline content, then we can fold the inline content back together.
+    RenderObject* prev = oldChild.previousSibling();
+    RenderObject* next = oldChild.nextSibling();
     bool canMergeAnonymousBlocks = canMergeContiguousAnonymousBlocks(oldChild, prev, next);
     if (canMergeAnonymousBlocks && prev && next) {
         prev->setNeedsLayoutAndPrefWidthsRecalc();
-        RenderBlock* nextBlock = toRenderBlock(next);
-        RenderBlock* prevBlock = toRenderBlock(prev);
+        RenderBlock& nextBlock = downcast<RenderBlock>(*next);
+        RenderBlock& prevBlock = downcast<RenderBlock>(*prev);
        
         if (prev->childrenInline() != next->childrenInline()) {
-            RenderBlock* inlineChildrenBlock = prev->childrenInline() ? prevBlock : nextBlock;
-            RenderBlock* blockChildrenBlock = prev->childrenInline() ? nextBlock : prevBlock;
+            RenderBlock& inlineChildrenBlock = prev->childrenInline() ? prevBlock : nextBlock;
+            RenderBlock& blockChildrenBlock = prev->childrenInline() ? nextBlock : prevBlock;
             
             // Place the inline children block inside of the block children block instead of deleting it.
             // In order to reuse it, we have to reset it to just be a generic anonymous block.  Make sure
             // to clear out inherited column properties by just making a new style, and to also clear the
             // column span flag if it is set.
-            ASSERT(!inlineChildrenBlock->continuation());
-            RefPtr<RenderStyle> newStyle = RenderStyle::createAnonymousStyleWithDisplay(style(), BLOCK);
+            ASSERT(!inlineChildrenBlock.continuation());
             // Cache this value as it might get changed in setStyle() call.
-            bool inlineChildrenBlockHasLayer = inlineChildrenBlock->hasLayer();
-            inlineChildrenBlock->setStyle(newStyle);
-            children()->removeChildNode(this, inlineChildrenBlock, inlineChildrenBlockHasLayer);
+            bool inlineChildrenBlockHasLayer = inlineChildrenBlock.hasLayer();
+            inlineChildrenBlock.setStyle(RenderStyle::createAnonymousStyleWithDisplay(&style(), BLOCK));
+            removeChildInternal(inlineChildrenBlock, inlineChildrenBlockHasLayer ? NotifyChildren : DontNotifyChildren);
             
             // Now just put the inlineChildrenBlock inside the blockChildrenBlock.
-            blockChildrenBlock->children()->insertChildNode(blockChildrenBlock, inlineChildrenBlock, prev == inlineChildrenBlock ? blockChildrenBlock->firstChild() : 0,
-                                                            inlineChildrenBlockHasLayer || blockChildrenBlock->hasLayer());
+            RenderObject* beforeChild = prev == &inlineChildrenBlock ? blockChildrenBlock.firstChild() : nullptr;
+            blockChildrenBlock.insertChildInternal(&inlineChildrenBlock, beforeChild,
+                (inlineChildrenBlockHasLayer || blockChildrenBlock.hasLayer()) ? NotifyChildren : DontNotifyChildren);
             next->setNeedsLayoutAndPrefWidthsRecalc();
             
             // inlineChildrenBlock got reparented to blockChildrenBlock, so it is no longer a child
             // of "this". we null out prev or next so that is not used later in the function.
-            if (inlineChildrenBlock == prevBlock)
-                prev = 0;
+            if (&inlineChildrenBlock == &prevBlock)
+                prev = nullptr;
             else
-                next = 0;
+                next = nullptr;
         } else {
             // Take all the children out of the |next| block and put them in
             // the |prev| block.
-            nextBlock->moveAllChildrenIncludingFloatsTo(prevBlock, nextBlock->hasLayer() || prevBlock->hasLayer());
+            nextBlock.moveAllChildrenIncludingFloatsTo(prevBlock, nextBlock.hasLayer() || prevBlock.hasLayer());
             
             // Delete the now-empty block's lines and nuke it.
-            nextBlock->deleteLineBoxTree();
-            nextBlock->destroy();
-            next = 0;
+            nextBlock.deleteLines();
+            nextBlock.destroy();
+            next = nullptr;
         }
     }
 
+    invalidateLineLayoutPath();
+
     RenderBox::removeChild(oldChild);
 
     RenderObject* child = prev ? prev : next;
-    if (canMergeAnonymousBlocks && child && !child->previousSibling() && !child->nextSibling() && canCollapseAnonymousBlockChild()) {
+    if (canMergeAnonymousBlocks && child && !child->previousSibling() && !child->nextSibling() && canDropAnonymousBlockChild()) {
         // The removal has knocked us down to containing only a single anonymous
-        // box.  We can go ahead and pull the content right back up into our
-        // box.
-        collapseAnonymousBoxChild(this, child);
-    } else if (((prev && prev->isAnonymousBlock()) || (next && next->isAnonymousBlock())) && canCollapseAnonymousBlockChild()) {
+        // box. We can pull the content right back up into our box.
+        dropAnonymousBoxChild(*this, downcast<RenderBlock>(*child));
+    } else if (((prev && prev->isAnonymousBlock()) || (next && next->isAnonymousBlock())) && canDropAnonymousBlockChild()) {
         // It's possible that the removal has knocked us down to a single anonymous
-        // block with pseudo-style element siblings (e.g. first-letter). If these
-        // are floating, then we need to pull the content up also.
-        RenderBlock* anonBlock = toRenderBlock((prev && prev->isAnonymousBlock()) ? prev : next);
-        if ((anonBlock->previousSibling() || anonBlock->nextSibling())
-            && (!anonBlock->previousSibling() || (anonBlock->previousSibling()->style()->styleType() != NOPSEUDO && anonBlock->previousSibling()->isFloating() && !anonBlock->previousSibling()->previousSibling()))
-            && (!anonBlock->nextSibling() || (anonBlock->nextSibling()->style()->styleType() != NOPSEUDO && anonBlock->nextSibling()->isFloating() && !anonBlock->nextSibling()->nextSibling()))) {
-            collapseAnonymousBoxChild(this, anonBlock);
+        // block with floating siblings.
+        RenderBlock& anonBlock = downcast<RenderBlock>((prev && prev->isAnonymousBlock()) ? *prev : *next);
+        if (canDropAnonymousBlock(anonBlock)) {
+            bool dropAnonymousBlock = true;
+            for (auto& sibling : childrenOfType<RenderObject>(*this)) {
+                if (&sibling == &anonBlock)
+                    continue;
+                if (!sibling.isFloating()) {
+                    dropAnonymousBlock = false;
+                    break;
+                }
+            }
+            if (dropAnonymousBlock)
+                dropAnonymousBoxChild(*this, anonBlock);
         }
     }
 
     if (!firstChild()) {
         // If this was our last child be sure to clear out our line boxes.
         if (childrenInline())
-            deleteLineBoxTree();
+            deleteLines();
 
         // If we are an empty anonymous block in the continuation chain,
         // we need to remove ourself and fix the continuation chain.
-        if (!beingDestroyed() && isAnonymousBlockContinuation() && !oldChild->isListMarker()) {
-            RenderObject* containingBlockIgnoringAnonymous = containingBlock();
+        if (!beingDestroyed() && isAnonymousBlockContinuation() && !oldChild.isListMarker()) {
+            auto containingBlockIgnoringAnonymous = containingBlock();
             while (containingBlockIgnoringAnonymous && containingBlockIgnoringAnonymous->isAnonymousBlock())
                 containingBlockIgnoringAnonymous = containingBlockIgnoringAnonymous->containingBlock();
-            for (RenderObject* curr = this; curr; curr = curr->previousInPreOrder(containingBlockIgnoringAnonymous)) {
-                if (curr->virtualContinuation() != this)
+            for (RenderObject* current = this; current; current = current->previousInPreOrder(containingBlockIgnoringAnonymous)) {
+                if (current->virtualContinuation() != this)
                     continue;
 
                 // Found our previous continuation. We just need to point it to
                 // |this|'s next continuation.
                 RenderBoxModelObject* nextContinuation = continuation();
-                if (curr->isRenderInline())
-                    toRenderInline(curr)->setContinuation(nextContinuation);
-                else if (curr->isRenderBlock())
-                    toRenderBlock(curr)->setContinuation(nextContinuation);
+                if (is<RenderInline>(*current))
+                    downcast<RenderInline>(*current).setContinuation(nextContinuation);
+                else if (is<RenderBlock>(*current))
+                    downcast<RenderBlock>(*current).setContinuation(nextContinuation);
                 else
                     ASSERT_NOT_REACHED();
 
                 break;
             }
-            setContinuation(0);
+            setContinuation(nullptr);
             destroy();
         }
     }
 }
 
+bool RenderBlock::childrenPreventSelfCollapsing() const
+{
+    // Whether or not we collapse is dependent on whether all our normal flow children
+    // are also self-collapsing.
+    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
+        if (child->isFloatingOrOutOfFlowPositioned())
+            continue;
+        if (!child->isSelfCollapsingBlock())
+            return true;
+    }
+    return false;
+}
+
 bool RenderBlock::isSelfCollapsingBlock() const
 {
     // We are not self-collapsing if we
@@ -1331,88 +836,98 @@ bool RenderBlock::isSelfCollapsingBlock() const
     // (e) have specified that one of our margins can't collapse using a CSS extension
     if (logicalHeight() > 0
         || isTable() || borderAndPaddingLogicalHeight()
-        || style()->logicalMinHeight().isPositive()
-        || style()->marginBeforeCollapse() == MSEPARATE || style()->marginAfterCollapse() == MSEPARATE)
+        || style().logicalMinHeight().isPositive()
+        || style().marginBeforeCollapse() == MSEPARATE || style().marginAfterCollapse() == MSEPARATE)
         return false;
 
-    Length logicalHeightLength = style()->logicalHeight();
+    Length logicalHeightLength = style().logicalHeight();
     bool hasAutoHeight = logicalHeightLength.isAuto();
-    if (logicalHeightLength.isPercent() && !document()->inQuirksMode()) {
+    if (logicalHeightLength.isPercentOrCalculated() && !document().inQuirksMode()) {
         hasAutoHeight = true;
-        for (RenderBlock* cb = containingBlock(); !cb->isRenderView(); cb = cb->containingBlock()) {
-            if (cb->style()->logicalHeight().isFixed() || cb->isTableCell())
+        for (RenderBlock* cb = containingBlock(); cb && !is<RenderView>(*cb); cb = cb->containingBlock()) {
+            if (cb->style().logicalHeight().isFixed() || cb->isTableCell())
                 hasAutoHeight = false;
         }
     }
 
     // If the height is 0 or auto, then whether or not we are a self-collapsing block depends
     // on whether we have content that is all self-collapsing or not.
-    if (hasAutoHeight || ((logicalHeightLength.isFixed() || logicalHeightLength.isPercent()) && logicalHeightLength.isZero())) {
-        // If the block has inline children, see if we generated any line boxes.  If we have any
-        // line boxes, then we can't be self-collapsing, since we have content.
-        if (childrenInline())
-            return !firstLineBox();
-        
-        // Whether or not we collapse is dependent on whether all our normal flow children
-        // are also self-collapsing.
-        for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
-            if (child->isFloatingOrOutOfFlowPositioned())
-                continue;
-            if (!child->isSelfCollapsingBlock())
-                return false;
-        }
-        return true;
-    }
+    if (hasAutoHeight || ((logicalHeightLength.isFixed() || logicalHeightLength.isPercentOrCalculated()) && logicalHeightLength.isZero()))
+        return !childrenPreventSelfCollapsing();
+
     return false;
 }
 
-void RenderBlock::startDelayUpdateScrollInfo()
+static inline UpdateScrollInfoAfterLayoutTransaction* currentUpdateScrollInfoAfterLayoutTransaction()
 {
-    if (gDelayUpdateScrollInfo == 0) {
-        ASSERT(!gDelayedUpdateScrollInfoSet);
-        gDelayedUpdateScrollInfoSet = new DelayedUpdateScrollInfoSet;
-    }
-    ASSERT(gDelayedUpdateScrollInfoSet);
-    ++gDelayUpdateScrollInfo;
+    if (!updateScrollInfoAfterLayoutTransactionStack())
+        return nullptr;
+    return &updateScrollInfoAfterLayoutTransactionStack()->last();
+}
+
+void RenderBlock::beginUpdateScrollInfoAfterLayoutTransaction()
+{
+    if (!updateScrollInfoAfterLayoutTransactionStack())
+        updateScrollInfoAfterLayoutTransactionStack() = std::make_unique<DelayedUpdateScrollInfoStack>();
+    if (updateScrollInfoAfterLayoutTransactionStack()->isEmpty() || currentUpdateScrollInfoAfterLayoutTransaction()->view != &view())
+        updateScrollInfoAfterLayoutTransactionStack()->append(UpdateScrollInfoAfterLayoutTransaction(view()));
+    ++currentUpdateScrollInfoAfterLayoutTransaction()->nestedCount;
 }
 
-void RenderBlock::finishDelayUpdateScrollInfo()
+void RenderBlock::endAndCommitUpdateScrollInfoAfterLayoutTransaction()
 {
-    --gDelayUpdateScrollInfo;
-    ASSERT(gDelayUpdateScrollInfo >= 0);
-    if (gDelayUpdateScrollInfo == 0) {
-        ASSERT(gDelayedUpdateScrollInfoSet);
+    UpdateScrollInfoAfterLayoutTransaction* transaction = currentUpdateScrollInfoAfterLayoutTransaction();
+    ASSERT(transaction);
+    ASSERT(transaction->view == &view());
+    if (--transaction->nestedCount)
+        return;
 
-        OwnPtr<DelayedUpdateScrollInfoSet> infoSet(adoptPtr(gDelayedUpdateScrollInfoSet));
-        gDelayedUpdateScrollInfoSet = 0;
+    // Calling RenderLayer::updateScrollInfoAfterLayout() may cause its associated block to layout again and
+    // updates its scroll info (i.e. call RenderBlock::updateScrollInfoAfterLayout()). We remove |transaction|
+    // from the transaction stack to ensure that all subsequent calls to RenderBlock::updateScrollInfoAfterLayout()
+    // are dispatched immediately. That is, to ensure that such subsequent calls aren't added to |transaction|
+    // while we are processing it.
+    Vector<RenderBlock*> blocksToUpdate;
+    copyToVector(transaction->blocks, blocksToUpdate);
+    updateScrollInfoAfterLayoutTransactionStack()->removeLast();
+    if (updateScrollInfoAfterLayoutTransactionStack()->isEmpty())
+        updateScrollInfoAfterLayoutTransactionStack() = nullptr;
 
-        for (DelayedUpdateScrollInfoSet::iterator it = infoSet->begin(); it != infoSet->end(); ++it) {
-            RenderBlock* block = *it;
-            if (block->hasOverflowClip()) {
-                block->layer()->updateScrollInfoAfterLayout();
-                block->clearLayoutOverflow();
-            }
-        }
+    for (auto* block : blocksToUpdate) {
+        ASSERT(block->hasOverflowClip());
+        block->layer()->updateScrollInfoAfterLayout();
+        block->clearLayoutOverflow();
+    }
+}
+
+void RenderBlock::removeFromUpdateScrollInfoAfterLayoutTransaction()
+{
+    if (UNLIKELY(updateScrollInfoAfterLayoutTransactionStack().get() != 0)) {
+        UpdateScrollInfoAfterLayoutTransaction* transaction = currentUpdateScrollInfoAfterLayoutTransaction();
+        ASSERT(transaction);
+        if (transaction->view == &view())
+            transaction->blocks.remove(this);
     }
 }
 
 void RenderBlock::updateScrollInfoAfterLayout()
 {
-    if (hasOverflowClip()) {
-        if (style()->isFlippedBlocksWritingMode()) {
-            // FIXME: https://bugs.webkit.org/show_bug.cgi?id=97937
-            // Workaround for now. We cannot delay the scroll info for overflow
-            // for items with opposite writing directions, as the contents needs
-            // to overflow in that direction
-            layer()->updateScrollInfoAfterLayout();
+    if (!hasOverflowClip())
+        return;
+    
+    // FIXME: https://bugs.webkit.org/show_bug.cgi?id=97937
+    // Workaround for now. We cannot delay the scroll info for overflow
+    // for items with opposite writing directions, as the contents needs
+    // to overflow in that direction
+    if (!style().isFlippedBlocksWritingMode()) {
+        UpdateScrollInfoAfterLayoutTransaction* transaction = currentUpdateScrollInfoAfterLayoutTransaction();
+        if (transaction && transaction->view == &view()) {
+            transaction->blocks.add(this);
             return;
         }
-
-        if (gDelayUpdateScrollInfo)
-            gDelayedUpdateScrollInfoSet->add(this);
-        else
-            layer()->updateScrollInfoAfterLayout();
     }
+    if (layer())
+        layer()->updateScrollInfoAfterLayout();
 }
 
 void RenderBlock::layout()
@@ -1429,361 +944,76 @@ void RenderBlock::layout()
     
     // It's safe to check for control clip here, since controls can never be table cells.
     // If we have a lightweight clip, there can never be any overflow from children.
-    if (hasControlClip() && m_overflow && !gDelayUpdateScrollInfo)
+    UpdateScrollInfoAfterLayoutTransaction* transaction = currentUpdateScrollInfoAfterLayoutTransaction();
+    bool isDelayingUpdateScrollInfoAfterLayoutInView = transaction && transaction->view == &view();
+    if (hasControlClip() && m_overflow && !isDelayingUpdateScrollInfoAfterLayoutInView)
         clearLayoutOverflow();
 
     invalidateBackgroundObscurationStatus();
 }
 
-#if ENABLE(CSS_SHAPES)
-void RenderBlock::updateShapeInsideInfoAfterStyleChange(const ShapeValue* shapeInside, const ShapeValue* oldShapeInside)
+static RenderBlockRareData* getBlockRareData(const RenderBlock* block)
 {
-    // FIXME: A future optimization would do a deep comparison for equality.
-    if (shapeInside == oldShapeInside)
-        return;
-
-    if (shapeInside) {
-        ShapeInsideInfo* shapeInsideInfo = ensureShapeInsideInfo();
-        shapeInsideInfo->dirtyShapeSize();
-    } else {
-        setShapeInsideInfo(nullptr);
-        markShapeInsideDescendantsForLayout();
-    }
+    return gRareDataMap ? gRareDataMap->get(block) : nullptr;
 }
 
-void RenderBlock::markShapeInsideDescendantsForLayout()
+static RenderBlockRareData& ensureBlockRareData(const RenderBlock* block)
 {
-    if (!everHadLayout())
-        return;
-    if (childrenInline()) {
-        setNeedsLayout(true);
-        return;
-    }
-    for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
-        if (!child->isRenderBlock())
-            continue;
-        RenderBlock* childBlock = toRenderBlock(child);
-        childBlock->markShapeInsideDescendantsForLayout();
-    }
-}
-#endif
-
-static inline bool shapeInfoRequiresRelayout(const RenderBlock* block)
-{
-#if !ENABLE(CSS_SHAPES)
-    return false;
-#else
-    ShapeInsideInfo* info = block->shapeInsideInfo();
-    if (info)
-        info->setNeedsLayout(info->shapeSizeDirty());
-    else
-        info = block->layoutShapeInsideInfo();
-    return info && info->needsLayout();
-#endif
-}
-
-bool RenderBlock::updateRegionsAndShapesBeforeChildLayout(RenderFlowThread* flowThread)
-{
-#if ENABLE(CSS_SHAPES)
-    if (!flowThread && !shapeInsideInfo())
-#else
-    if (!flowThread)
-#endif
-        return shapeInfoRequiresRelayout(this);
-
-    LayoutUnit oldHeight = logicalHeight();
-    LayoutUnit oldTop = logicalTop();
-
-    // Compute the maximum logical height content may cause this block to expand to
-    // FIXME: These should eventually use the const computeLogicalHeight rather than updateLogicalHeight
-    setLogicalHeight(RenderFlowThread::maxLogicalHeight());
-    updateLogicalHeight();
-
-#if ENABLE(CSS_SHAPES)
-    computeShapeSize();
-#endif
-
-    // Set our start and end regions. No regions above or below us will be considered by our children. They are
-    // effectively clamped to our region range.
-    computeRegionRangeForBlock(flowThread);
-
-    setLogicalHeight(oldHeight);
-    setLogicalTop(oldTop);
-    
-    return shapeInfoRequiresRelayout(this);
-}
-
-#if ENABLE(CSS_SHAPES)
-void RenderBlock::computeShapeSize()
-{
-    ShapeInsideInfo* shapeInsideInfo = this->shapeInsideInfo();
-    if (shapeInsideInfo) {
-        bool percentageLogicalHeightResolvable = percentageLogicalHeightIsResolvableFromBlock(this, false);
-        shapeInsideInfo->setShapeSize(logicalWidth(), percentageLogicalHeightResolvable ? logicalHeight() : LayoutUnit());
-    }
-}
-#endif
-
-void RenderBlock::updateRegionsAndShapesAfterChildLayout(RenderFlowThread* flowThread, bool heightChanged)
-{
-#if ENABLE(CSS_SHAPES)
-    // A previous sibling has changed dimension, so we need to relayout the shape with the content
-    ShapeInsideInfo* shapeInsideInfo = layoutShapeInsideInfo();
-    if (heightChanged && shapeInsideInfo)
-        shapeInsideInfo->dirtyShapeSize();
-#else
-    UNUSED_PARAM(heightChanged);
-#endif
-    computeRegionRangeForBlock(flowThread);
+    if (!gRareDataMap)
+        gRareDataMap = new RenderBlockRareDataMap;
+    
+    auto& rareData = gRareDataMap->add(block, nullptr).iterator->value;
+    if (!rareData)
+        rareData = std::make_unique<RenderBlockRareData>();
+    return *rareData.get();
 }
 
-void RenderBlock::computeRegionRangeForBlock(RenderFlowThread* flowThread)
+void RenderBlock::preparePaginationBeforeBlockLayout(bool& relayoutChildren)
 {
+    // Regions changing widths can force us to relayout our children.
+    RenderFlowThread* flowThread = flowThreadContainingBlock();
     if (flowThread)
-        flowThread->setRegionRangeForBox(this, offsetFromLogicalTopOfFirstPage());
+        flowThread->logicalWidthChangedInRegionsForBlock(this, relayoutChildren);
 }
 
-bool RenderBlock::updateLogicalWidthAndColumnWidth()
+bool RenderBlock::recomputeLogicalWidth()
 {
     LayoutUnit oldWidth = logicalWidth();
-    LayoutUnit oldColumnWidth = desiredColumnWidth();
-
+    
     updateLogicalWidth();
-    calcColumnWidth();
-
-    bool hasBorderOrPaddingLogicalWidthChanged = m_hasBorderOrPaddingLogicalWidthChanged;
-    m_hasBorderOrPaddingLogicalWidthChanged = false;
+    
+    bool hasBorderOrPaddingLogicalWidthChanged = this->hasBorderOrPaddingLogicalWidthChanged();
+    setHasBorderOrPaddingLogicalWidthChanged(false);
 
-    return oldWidth != logicalWidth() || oldColumnWidth != desiredColumnWidth() || hasBorderOrPaddingLogicalWidthChanged;
+    return oldWidth != logicalWidth() || hasBorderOrPaddingLogicalWidthChanged;
 }
 
-void RenderBlock::checkForPaginationLogicalHeightChange(LayoutUnit& pageLogicalHeight, bool& pageLogicalHeightChanged, bool& hasSpecifiedPageLogicalHeight)
+void RenderBlock::layoutBlock(bool, LayoutUnit)
 {
-    ColumnInfo* colInfo = columnInfo();
-    if (hasColumns()) {
-        if (!pageLogicalHeight) {
-            // We need to go ahead and set our explicit page height if one exists, so that we can
-            // avoid doing two layout passes.
-            updateLogicalHeight();
-            LayoutUnit columnHeight = isRenderView() ? view()->pageOrViewLogicalHeight() : contentLogicalHeight();
-            if (columnHeight > 0) {
-                pageLogicalHeight = columnHeight;
-                hasSpecifiedPageLogicalHeight = true;
-            }
-            setLogicalHeight(0);
-        }
-
-        if (colInfo->columnHeight() != pageLogicalHeight && everHadLayout())
-            pageLogicalHeightChanged = true;
-
-        colInfo->setColumnHeight(pageLogicalHeight);
-        
-        if (!hasSpecifiedPageLogicalHeight && !pageLogicalHeight)
-            colInfo->clearForcedBreaks();
-
-        colInfo->setPaginationUnit(paginationUnit());
-    } else if (isRenderFlowThread()) {
-        pageLogicalHeight = 1; // This is just a hack to always make sure we have a page logical height.
-        pageLogicalHeightChanged = toRenderFlowThread(this)->pageLogicalSizeChanged();
-    }
+    ASSERT_NOT_REACHED();
+    clearNeedsLayout();
 }
 
-void RenderBlock::layoutBlock(bool relayoutChildren, LayoutUnit pageLogicalHeight)
+void RenderBlock::addOverflowFromChildren()
 {
-    ASSERT(needsLayout());
-
-    if (isInline() && !isInlineBlockOrInlineTable()) // Inline <form>s inside various table elements can
-        return;                                      // cause us to come in here.  Just bail.
-
-    if (!relayoutChildren && simplifiedLayout())
-        return;
-
-    LayoutRepainter repainter(*this, checkForRepaintDuringLayout());
-
-    if (updateLogicalWidthAndColumnWidth())
-        relayoutChildren = true;
-
-    clearFloats();
-
-    LayoutUnit previousHeight = logicalHeight();
-    // FIXME: should this start out as borderAndPaddingLogicalHeight() + scrollbarLogicalHeight(),
-    // for consistency with other render classes?
-    setLogicalHeight(0);
-
-    bool pageLogicalHeightChanged = false;
-    bool hasSpecifiedPageLogicalHeight = false;
-    checkForPaginationLogicalHeightChange(pageLogicalHeight, pageLogicalHeightChanged, hasSpecifiedPageLogicalHeight);
-
-    RenderView* renderView = view();
-    RenderStyle* styleToUse = style();
-    LayoutStateMaintainer statePusher(renderView, this, locationOffset(), hasColumns() || hasTransform() || hasReflection() || styleToUse->isFlippedBlocksWritingMode(), pageLogicalHeight, pageLogicalHeightChanged, columnInfo());
-
-    // Regions changing widths can force us to relayout our children.
-    RenderFlowThread* flowThread = flowThreadContainingBlock();
-    if (logicalWidthChangedInRegions(flowThread))
-        relayoutChildren = true;
-    if (updateRegionsAndShapesBeforeChildLayout(flowThread))
-        relayoutChildren = true;
-
-    // We use four values, maxTopPos, maxTopNeg, maxBottomPos, and maxBottomNeg, to track
-    // our current maximal positive and negative margins.  These values are used when we
-    // are collapsed with adjacent blocks, so for example, if you have block A and B
-    // collapsing together, then you'd take the maximal positive margin from both A and B
-    // and subtract it from the maximal negative margin from both A and B to get the
-    // true collapsed margin.  This algorithm is recursive, so when we finish layout()
-    // our block knows its current maximal positive/negative values.
-    //
-    // Start out by setting our margin values to our current margins.  Table cells have
-    // no margins, so we don't fill in the values for table cells.
-    bool isCell = isTableCell();
-    if (!isCell) {
-        initMaxMarginValues();
-        
-        setHasMarginBeforeQuirk(styleToUse->hasMarginBeforeQuirk());
-        setHasMarginAfterQuirk(styleToUse->hasMarginAfterQuirk());
-        setPaginationStrut(0);
-    }
-
-    LayoutUnit repaintLogicalTop = 0;
-    LayoutUnit repaintLogicalBottom = 0;
-    LayoutUnit maxFloatLogicalBottom = 0;
-    if (!firstChild() && !isAnonymousBlock())
-        setChildrenInline(true);
     if (childrenInline())
-        layoutInlineChildren(relayoutChildren, repaintLogicalTop, repaintLogicalBottom);
+        addOverflowFromInlineChildren();
     else
-        layoutBlockChildren(relayoutChildren, maxFloatLogicalBottom);
-
-    // Expand our intrinsic height to encompass floats.
-    LayoutUnit toAdd = borderAndPaddingAfter() + scrollbarLogicalHeight();
-    if (lowestFloatLogicalBottom() > (logicalHeight() - toAdd) && expandsToEncloseOverhangingFloats())
-        setLogicalHeight(lowestFloatLogicalBottom() + toAdd);
-    
-    if (relayoutForPagination(hasSpecifiedPageLogicalHeight, pageLogicalHeight, statePusher))
-        return;
-
-    // Calculate our new height.
-    LayoutUnit oldHeight = logicalHeight();
-    LayoutUnit oldClientAfterEdge = clientLogicalBottom();
-
-    // Before updating the final size of the flow thread make sure a forced break is applied after the content.
-    // This ensures the size information is correctly computed for the last auto-height region receiving content.
-    if (isRenderFlowThread())
-        toRenderFlowThread(this)->applyBreakAfterContent(oldClientAfterEdge);
-
-    updateLogicalHeight();
-    LayoutUnit newHeight = logicalHeight();
-    if (oldHeight != newHeight) {
-        if (oldHeight > newHeight && maxFloatLogicalBottom > newHeight && !childrenInline()) {
-            // One of our children's floats may have become an overhanging float for us. We need to look for it.
-            for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
-                if (child->isBlockFlow() && !child->isFloatingOrOutOfFlowPositioned()) {
-                    RenderBlock* block = toRenderBlock(child);
-                    if (block->lowestFloatLogicalBottom() + block->logicalTop() > newHeight)
-                        addOverhangingFloats(block, false);
-                }
-            }
-        }
-    }
-
-    bool heightChanged = (previousHeight != newHeight);
-    if (heightChanged)
-        relayoutChildren = true;
-
-    layoutPositionedObjects(relayoutChildren || isRoot());
-
-    updateRegionsAndShapesAfterChildLayout(flowThread, heightChanged);
-
-    // Add overflow from children (unless we're multi-column, since in that case all our child overflow is clipped anyway).
-    computeOverflow(oldClientAfterEdge);
+        addOverflowFromBlockChildren();
     
-    statePusher.pop();
-
-    fitBorderToLinesIfNeeded();
-
-    if (renderView->layoutState()->m_pageLogicalHeight)
-        setPageLogicalOffset(renderView->layoutState()->pageLogicalOffset(this, logicalTop()));
-
-    updateLayerTransform();
-
-    // Update our scroll information if we're overflow:auto/scroll/hidden now that we know if
-    // we overflow or not.
-    updateScrollInfoAfterLayout();
-
-    // FIXME: This repaint logic should be moved into a separate helper function!
-    // Repaint with our new bounds if they are different from our old bounds.
-    bool didFullRepaint = repainter.repaintAfterLayout();
-    if (!didFullRepaint && repaintLogicalTop != repaintLogicalBottom && (styleToUse->visibility() == VISIBLE || enclosingLayer()->hasVisibleContent())) {
-        // FIXME: We could tighten up the left and right invalidation points if we let layoutInlineChildren fill them in based off the particular lines
-        // it had to lay out.  We wouldn't need the hasOverflowClip() hack in that case either.
-        LayoutUnit repaintLogicalLeft = logicalLeftVisualOverflow();
-        LayoutUnit repaintLogicalRight = logicalRightVisualOverflow();
-        if (hasOverflowClip()) {
-            // If we have clipped overflow, we should use layout overflow as well, since visual overflow from lines didn't propagate to our block's overflow.
-            // Note the old code did this as well but even for overflow:visible.  The addition of hasOverflowClip() at least tightens up the hack a bit.
-            // layoutInlineChildren should be patched to compute the entire repaint rect.
-            repaintLogicalLeft = min(repaintLogicalLeft, logicalLeftLayoutOverflow());
-            repaintLogicalRight = max(repaintLogicalRight, logicalRightLayoutOverflow());
-        }
-        
-        LayoutRect repaintRect;
-        if (isHorizontalWritingMode())
-            repaintRect = LayoutRect(repaintLogicalLeft, repaintLogicalTop, repaintLogicalRight - repaintLogicalLeft, repaintLogicalBottom - repaintLogicalTop);
-        else
-            repaintRect = LayoutRect(repaintLogicalTop, repaintLogicalLeft, repaintLogicalBottom - repaintLogicalTop, repaintLogicalRight - repaintLogicalLeft);
-
-        // The repaint rect may be split across columns, in which case adjustRectForColumns() will return the union.
-        adjustRectForColumns(repaintRect);
-
-        repaintRect.inflate(maximalOutlineSize(PaintPhaseOutline));
-        
-        if (hasOverflowClip()) {
-            // Adjust repaint rect for scroll offset
-            repaintRect.move(-scrolledContentOffset());
-
-            // Don't allow this rect to spill out of our overflow box.
-            repaintRect.intersect(LayoutRect(LayoutPoint(), size()));
-        }
-
-        // Make sure the rect is still non-empty after intersecting for overflow above
-        if (!repaintRect.isEmpty()) {
-            repaintRectangle(repaintRect); // We need to do a partial repaint of our content.
-            if (hasReflection())
-                repaintRectangle(reflectedRect(repaintRect));
-        }
-    }
-
-    setNeedsLayout(false);
-}
-
-void RenderBlock::addOverflowFromChildren()
-{
-    if (!hasColumns()) {
-        if (childrenInline())
-            addOverflowFromInlineChildren();
-        else
-            addOverflowFromBlockChildren();
-    } else {
-        ColumnInfo* colInfo = columnInfo();
-        if (columnCount(colInfo)) {
-            LayoutRect lastRect = columnRectAt(colInfo, columnCount(colInfo) - 1);
-            addLayoutOverflow(lastRect);
-            if (!hasOverflowClip())
-                addVisualOverflow(lastRect);
-        }
+    // If this block is flowed inside a flow thread, make sure its overflow is propagated to the containing regions.
+    if (m_overflow) {
+        if (RenderFlowThread* containingFlowThread = flowThreadContainingBlock())
+            containingFlowThread->addRegionsVisualOverflow(this, m_overflow->visualOverflowRect());
     }
 }
 
-void RenderBlock::computeOverflow(LayoutUnit oldClientAfterEdge, bool recomputeFloats)
+void RenderBlock::computeOverflow(LayoutUnit oldClientAfterEdge, bool)
 {
-    m_overflow.clear();
-
+    clearOverflow();
     // Add overflow from children.
     addOverflowFromChildren();
 
-    if (!hasColumns() && (recomputeFloats || isRoot() || expandsToEncloseOverhangingFloats() || hasSelfPaintingLayer()))
-        addOverflowFromFloats();
-
     // Add in the overflow from positioned objects.
     addOverflowFromPositionedObjects();
 
@@ -1791,33 +1021,22 @@ void RenderBlock::computeOverflow(LayoutUnit oldClientAfterEdge, bool recomputeF
         // When we have overflow clip, propagate the original spillout since it will include collapsed bottom margins
         // and bottom padding.  Set the axis we don't care about to be 1, since we want this overflow to always
         // be considered reachable.
-        LayoutRect clientRect(clientBoxRect());
+        LayoutRect clientRect(flippedClientBoxRect());
         LayoutRect rectToApply;
         if (isHorizontalWritingMode())
-            rectToApply = LayoutRect(clientRect.x(), clientRect.y(), 1, max<LayoutUnit>(0, oldClientAfterEdge - clientRect.y()));
+            rectToApply = LayoutRect(clientRect.x(), clientRect.y(), 1, std::max<LayoutUnit>(0, oldClientAfterEdge - clientRect.y()));
         else
-            rectToApply = LayoutRect(clientRect.x(), clientRect.y(), max<LayoutUnit>(0, oldClientAfterEdge - clientRect.x()), 1);
+            rectToApply = LayoutRect(clientRect.x(), clientRect.y(), std::max<LayoutUnit>(0, oldClientAfterEdge - clientRect.x()), 1);
         addLayoutOverflow(rectToApply);
         if (hasRenderOverflow())
             m_overflow->setLayoutClientAfterEdge(oldClientAfterEdge);
     }
         
-    // Allow our overflow to catch cases where the caret in an empty editable element with negative text indent needs to get painted.
-    LayoutUnit textIndent = textIndentOffset();
-    if (textIndent < 0) {
-        LayoutRect clientRect(clientBoxRect());
-        LayoutRect rectToApply = LayoutRect(clientRect.x() + min<LayoutUnit>(0, textIndent), clientRect.y(), clientRect.width() - min<LayoutUnit>(0, textIndent), clientRect.height());
-        addVisualOverflow(rectToApply);
-    }
-
-    // Add visual overflow from box-shadow and border-image-outset.
+    // Add visual overflow from box-shadow, border-image-outset and outline.
     addVisualEffectOverflow();
 
     // Add visual overflow from theme.
     addVisualOverflowFromTheme();
-
-    if (isRenderNamedFlowThread())
-        toRenderNamedFlowThread(this)->computeOversetStateForRegions(oldClientAfterEdge);
 }
 
 void RenderBlock::clearLayoutOverflow()
@@ -1826,7 +1045,8 @@ void RenderBlock::clearLayoutOverflow()
         return;
     
     if (visualOverflowRect() == borderBoxRect()) {
-        m_overflow.clear();
+        // FIXME: Implement complete solution for regions overflow.
+        clearOverflow();
         return;
     }
     
@@ -1835,41 +1055,25 @@ void RenderBlock::clearLayoutOverflow()
 
 void RenderBlock::addOverflowFromBlockChildren()
 {
-    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
+    for (auto* child = firstChildBox(); child; child = child->nextSiblingBox()) {
         if (!child->isFloatingOrOutOfFlowPositioned())
             addOverflowFromChild(child);
     }
 }
 
-void RenderBlock::addOverflowFromFloats()
-{
-    if (!m_floatingObjects)
-        return;
-
-    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    FloatingObjectSetIterator end = floatingObjectSet.end();
-    for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-        FloatingObject* r = *it;
-        if (r->isDescendant())
-            addOverflowFromChild(r->m_renderer, IntSize(xPositionForFloatIncludingMargin(r), yPositionForFloatIncludingMargin(r)));
-    }
-}
-
 void RenderBlock::addOverflowFromPositionedObjects()
 {
     TrackedRendererListHashSet* positionedDescendants = positionedObjects();
     if (!positionedDescendants)
         return;
 
-    RenderBox* positionedObject;
-    TrackedRendererListHashSet::iterator end = positionedDescendants->end();
-    for (TrackedRendererListHashSet::iterator it = positionedDescendants->begin(); it != end; ++it) {
-        positionedObject = *it;
+    for (auto it = positionedDescendants->begin(), end = positionedDescendants->end(); it != end; ++it) {
+        RenderBox* positionedObject = *it;
         
         // Fixed positioned elements don't contribute to layout overflow, since they don't scroll with the content.
-        if (positionedObject->style()->position() != FixedPosition) {
+        if (positionedObject->style().position() != FixedPosition) {
             LayoutUnit x = positionedObject->x();
-            if (style()->shouldPlaceBlockDirectionScrollbarOnLogicalLeft())
+            if (style().shouldPlaceBlockDirectionScrollbarOnLogicalLeft())
                 x -= verticalScrollbarWidth();
             addOverflowFromChild(positionedObject, LayoutSize(x, positionedObject->y()));
         }
@@ -1878,4068 +1082,1601 @@ void RenderBlock::addOverflowFromPositionedObjects()
 
 void RenderBlock::addVisualOverflowFromTheme()
 {
-    if (!style()->hasAppearance())
+    if (!style().hasAppearance())
         return;
 
-    IntRect inflatedRect = pixelSnappedBorderBoxRect();
-    theme()->adjustRepaintRect(this, inflatedRect);
-    addVisualOverflow(inflatedRect);
-}
+    FloatRect inflatedRect = borderBoxRect();
+    theme().adjustRepaintRect(*this, inflatedRect);
+    addVisualOverflow(snappedIntRect(LayoutRect(inflatedRect)));
 
-bool RenderBlock::expandsToEncloseOverhangingFloats() const
-{
-    return isInlineBlockOrInlineTable() || isFloatingOrOutOfFlowPositioned() || hasOverflowClip() || (parent() && parent()->isFlexibleBoxIncludingDeprecated())
-           || hasColumns() || isTableCell() || isTableCaption() || isFieldset() || isWritingModeRoot() || isRoot();
+    if (RenderFlowThread* flowThread = flowThreadContainingBlock())
+        flowThread->addRegionsVisualOverflowFromTheme(this);
 }
 
-void RenderBlock::adjustPositionedBlock(RenderBox* child, const MarginInfo& marginInfo)
+LayoutUnit RenderBlock::computeStartPositionDeltaForChildAvoidingFloats(const RenderBox& child, LayoutUnit childMarginStart, RenderRegion* region)
 {
-    bool isHorizontal = isHorizontalWritingMode();
-    bool hasStaticBlockPosition = child->style()->hasStaticBlockPosition(isHorizontal);
-    
-    LayoutUnit logicalTop = logicalHeight();
-    updateStaticInlinePositionForChild(child, logicalTop);
-
-    if (!marginInfo.canCollapseWithMarginBefore()) {
-        // Positioned blocks don't collapse margins, so add the margin provided by
-        // the container now. The child's own margin is added later when calculating its logical top.
-        LayoutUnit collapsedBeforePos = marginInfo.positiveMargin();
-        LayoutUnit collapsedBeforeNeg = marginInfo.negativeMargin();
-        logicalTop += collapsedBeforePos - collapsedBeforeNeg;
-    }
-    
-    RenderLayer* childLayer = child->layer();
-    if (childLayer->staticBlockPosition() != logicalTop) {
-        childLayer->setStaticBlockPosition(logicalTop);
-        if (hasStaticBlockPosition)
-            child->setChildNeedsLayout(true, MarkOnlyThis);
-    }
-}
+    LayoutUnit startPosition = startOffsetForContent(region);
 
-void RenderBlock::adjustFloatingBlock(const MarginInfo& marginInfo)
-{
-    // The float should be positioned taking into account the bottom margin
-    // of the previous flow.  We add that margin into the height, get the
-    // float positioned properly, and then subtract the margin out of the
-    // height again.  In the case of self-collapsing blocks, we always just
-    // use the top margins, since the self-collapsing block collapsed its
-    // own bottom margin into its top margin.
-    //
-    // Note also that the previous flow may collapse its margin into the top of
-    // our block.  If this is the case, then we do not add the margin in to our
-    // height when computing the position of the float.   This condition can be tested
-    // for by simply calling canCollapseWithMarginBefore.  See
-    // http://www.hixie.ch/tests/adhoc/css/box/block/margin-collapse/046.html for
-    // an example of this scenario.
-    LayoutUnit marginOffset = marginInfo.canCollapseWithMarginBefore() ? LayoutUnit() : marginInfo.margin();
-    setLogicalHeight(logicalHeight() + marginOffset);
-    positionNewFloats();
-    setLogicalHeight(logicalHeight() - marginOffset);
-}
-
-static void destroyRunIn(RenderBoxModelObject* runIn)
-{
-    ASSERT(runIn->isRunIn());
-    ASSERT(!runIn->firstChild());
-
-    // Delete our line box tree. This is needed as our children got moved
-    // and our line box tree is no longer valid.
-    if (runIn->isRenderBlock())
-        toRenderBlock(runIn)->deleteLineBoxTree();
-    else if (runIn->isRenderInline())
-        toRenderInline(runIn)->deleteLineBoxTree();
-    else
-        ASSERT_NOT_REACHED();
+    // Add in our start margin.
+    LayoutUnit oldPosition = startPosition + childMarginStart;
+    LayoutUnit newPosition = oldPosition;
+
+    LayoutUnit blockOffset = logicalTopForChild(child);
+    if (region)
+        blockOffset = std::max(blockOffset, blockOffset + (region->logicalTopForFlowThreadContent() - offsetFromLogicalTopOfFirstPage()));
+
+    LayoutUnit startOff = startOffsetForLineInRegion(blockOffset, DoNotIndentText, region, logicalHeightForChild(child));
+
+    if (style().textAlign() != WEBKIT_CENTER && !child.style().marginStartUsing(&style()).isAuto()) {
+        if (childMarginStart < 0)
+            startOff += childMarginStart;
+        newPosition = std::max(newPosition, startOff); // Let the float sit in the child's margin if it can fit.
+    } else if (startOff != startPosition)
+        newPosition = startOff + childMarginStart;
 
-    runIn->destroy();
+    return newPosition - oldPosition;
 }
 
-void RenderBlock::placeRunInIfNeeded(RenderObject* newChild)
+void RenderBlock::setLogicalLeftForChild(RenderBox& child, LayoutUnit logicalLeft, ApplyLayoutDeltaMode applyDelta)
 {
-    if (newChild->isRunIn())
-        moveRunInUnderSiblingBlockIfNeeded(newChild);
-    else if (RenderObject* prevSibling = newChild->previousSibling()) {
-        if (prevSibling->isRunIn())
-            moveRunInUnderSiblingBlockIfNeeded(prevSibling);
+    if (isHorizontalWritingMode()) {
+        if (applyDelta == ApplyLayoutDelta)
+            view().addLayoutDelta(LayoutSize(child.x() - logicalLeft, 0));
+        child.setX(logicalLeft);
+    } else {
+        if (applyDelta == ApplyLayoutDelta)
+            view().addLayoutDelta(LayoutSize(0, child.y() - logicalLeft));
+        child.setY(logicalLeft);
     }
 }
 
-RenderBoxModelObject* RenderBlock::createReplacementRunIn(RenderBoxModelObject* runIn)
+void RenderBlock::setLogicalTopForChild(RenderBox& child, LayoutUnit logicalTop, ApplyLayoutDeltaMode applyDelta)
 {
-    ASSERT(runIn->isRunIn());
-    ASSERT(runIn->node());
-
-    RenderBoxModelObject* newRunIn = 0;
-    if (!runIn->isRenderBlock())
-        newRunIn = new (renderArena()) RenderBlock(runIn->node());
-    else
-        newRunIn = new (renderArena()) RenderInline(toElement(runIn->node()));
-
-    runIn->node()->setRenderer(newRunIn);
-    newRunIn->setStyle(runIn->style());
-
-    runIn->moveAllChildrenTo(newRunIn, true);
-
-    return newRunIn;
+    if (isHorizontalWritingMode()) {
+        if (applyDelta == ApplyLayoutDelta)
+            view().addLayoutDelta(LayoutSize(0, child.y() - logicalTop));
+        child.setY(logicalTop);
+    } else {
+        if (applyDelta == ApplyLayoutDelta)
+            view().addLayoutDelta(LayoutSize(child.x() - logicalTop, 0));
+        child.setX(logicalTop);
+    }
 }
 
-void RenderBlock::moveRunInUnderSiblingBlockIfNeeded(RenderObject* runIn)
+void RenderBlock::updateBlockChildDirtyBitsBeforeLayout(bool relayoutChildren, RenderBox& child)
 {
-    ASSERT(runIn->isRunIn());
+    // FIXME: Technically percentage height objects only need a relayout if their percentage isn't going to be turned into
+    // an auto value. Add a method to determine this, so that we can avoid the relayout.
+    if (relayoutChildren || (child.hasRelativeLogicalHeight() && !isRenderView()))
+        child.setChildNeedsLayout(MarkOnlyThis);
 
-    // See if we have inline children. If the children aren't inline,
-    // then just treat the run-in as a normal block.
-    if (!runIn->childrenInline())
-        return;
+    // If relayoutChildren is set and the child has percentage padding or an embedded content box, we also need to invalidate the childs pref widths.
+    if (relayoutChildren && child.needsPreferredWidthsRecalculation())
+        child.setPreferredLogicalWidthsDirty(true, MarkOnlyThis);
+}
 
-    // FIXME: We don't handle non-block elements with run-in for now.
-    if (!runIn->isRenderBlock())
+void RenderBlock::dirtyForLayoutFromPercentageHeightDescendants()
+{
+    if (!gPercentHeightDescendantsMap)
         return;
 
-    // FIXME: We don't support run-ins with or as part of a continuation
-    // as it makes the back-and-forth placing complex.
-    if (runIn->isElementContinuation() || runIn->virtualContinuation())
+    TrackedRendererListHashSet* descendants = gPercentHeightDescendantsMap->get(this);
+    if (!descendants)
         return;
 
-    // Check if this node is allowed to run-in. E.g. <select> expects its renderer to
-    // be a RenderListBox or RenderMenuList, and hence cannot be a RenderInline run-in.
-    if (!runIn->canBeReplacedWithInlineRunIn())
-        return;
+    for (auto it = descendants->begin(), end = descendants->end(); it != end; ++it) {
+        RenderBox* box = *it;
+        while (box != this) {
+            if (box->normalChildNeedsLayout())
+                break;
+            box->setChildNeedsLayout(MarkOnlyThis);
+            
+            // If the width of an image is affected by the height of a child (e.g., an image with an aspect ratio),
+            // then we have to dirty preferred widths, since even enclosing blocks can become dirty as a result.
+            // (A horizontal flexbox that contains an inline image wrapped in an anonymous block for example.)
+            if (box->hasAspectRatio()) 
+                box->setPreferredLogicalWidthsDirty(true);
+            
+            box = box->containingBlock();
+            ASSERT(box);
+            if (!box)
+                break;
+        }
+    }
+}
 
-    RenderObject* curr = runIn->nextSibling();
-    if (!curr || !curr->isRenderBlock() || !curr->childrenInline())
-        return;
+void RenderBlock::simplifiedNormalFlowLayout()
+{
+    if (childrenInline()) {
+        ListHashSet<RootInlineBox*> lineBoxes;
+        for (InlineWalker walker(*this); !walker.atEnd(); walker.advance()) {
+            RenderObject& renderer = *walker.current();
+            if (!renderer.isOutOfFlowPositioned() && (renderer.isReplaced() || renderer.isFloating())) {
+                RenderBox& box = downcast<RenderBox>(renderer);
+                box.layoutIfNeeded();
+                if (box.inlineBoxWrapper())
+                    lineBoxes.add(&box.inlineBoxWrapper()->root());
+            } else if (is<RenderText>(renderer) || (is<RenderInline>(renderer) && !walker.atEndOfInline()))
+                renderer.clearNeedsLayout();
+        }
 
-    if (toRenderBlock(curr)->beingDestroyed())
-        return;
+        // FIXME: Glyph overflow will get lost in this case, but not really a big deal.
+        // FIXME: Find a way to invalidate the knownToHaveNoOverflow flag on the InlineBoxes.
+        GlyphOverflowAndFallbackFontsMap textBoxDataMap;                  
+        for (auto it = lineBoxes.begin(), end = lineBoxes.end(); it != end; ++it) {
+            RootInlineBox* box = *it;
+            box->computeOverflow(box->lineTop(), box->lineBottom(), textBoxDataMap);
+        }
+    } else {
+        for (auto* box = firstChildBox(); box; box = box->nextSiblingBox()) {
+            if (!box->isOutOfFlowPositioned())
+                box->layoutIfNeeded();
+        }
+    }
+}
 
-    // Per CSS3, "A run-in cannot run in to a block that already starts with a
-    // run-in or that itself is a run-in".
-    if (curr->isRunIn() || (curr->firstChild() && curr->firstChild()->isRunIn()))
-        return;
+bool RenderBlock::simplifiedLayout()
+{
+    if ((!posChildNeedsLayout() && !needsSimplifiedNormalFlowLayout()) || normalChildNeedsLayout() || selfNeedsLayout())
+        return false;
 
-    if (curr->isAnonymous() || curr->isFloatingOrOutOfFlowPositioned())
-        return;
+    LayoutStateMaintainer statePusher(view(), *this, locationOffset(), hasTransform() || hasReflection() || style().isFlippedBlocksWritingMode());
+    if (needsPositionedMovementLayout() && !tryLayoutDoingPositionedMovementOnly()) {
+        statePusher.pop();
+        return false;
+    }
 
-    RenderBoxModelObject* oldRunIn = toRenderBoxModelObject(runIn);
-    RenderBoxModelObject* newRunIn = createReplacementRunIn(oldRunIn);
-    destroyRunIn(oldRunIn);
+    // Lay out positioned descendants or objects that just need to recompute overflow.
+    if (needsSimplifiedNormalFlowLayout())
+        simplifiedNormalFlowLayout();
 
-    // Now insert the new child under |curr| block. Use addChild instead of insertChildNode
-    // since it handles correct placement of the children, especially where we cannot insert
-    // anything before the first child. e.g. details tag. See https://bugs.webkit.org/show_bug.cgi?id=58228.
-    curr->addChild(newRunIn, curr->firstChild());
+    // Make sure a forced break is applied after the content if we are a flow thread in a simplified layout.
+    // This ensures the size information is correctly computed for the last auto-height region receiving content.
+    if (is<RenderFlowThread>(*this))
+        downcast<RenderFlowThread>(*this).applyBreakAfterContent(clientLogicalBottom());
 
-    // Make sure that |this| get a layout since its run-in child moved.
-    curr->setNeedsLayoutAndPrefWidthsRecalc();
-}
+    // Lay out our positioned objects if our positioned child bit is set.
+    // Also, if an absolute position element inside a relative positioned container moves, and the absolute element has a fixed position
+    // child, neither the fixed element nor its container learn of the movement since posChildNeedsLayout() is only marked as far as the 
+    // relative positioned container. So if we can have fixed pos objects in our positioned objects list check if any of them
+    // are statically positioned and thus need to move with their absolute ancestors.
+    bool canContainFixedPosObjects = canContainFixedPositionObjects();
+    if (posChildNeedsLayout() || canContainFixedPosObjects)
+        layoutPositionedObjects(false, !posChildNeedsLayout() && canContainFixedPosObjects);
 
-bool RenderBlock::runInIsPlacedIntoSiblingBlock(RenderObject* runIn)
-{
-    ASSERT(runIn->isRunIn());
+    // Recompute our overflow information.
+    // FIXME: We could do better here by computing a temporary overflow object from layoutPositionedObjects and only
+    // updating our overflow if we either used to have overflow or if the new temporary object has overflow.
+    // For now just always recompute overflow.  This is no worse performance-wise than the old code that called rightmostPosition and
+    // lowestPosition on every relayout so it's not a regression.
+    // computeOverflow expects the bottom edge before we clamp our height. Since this information isn't available during
+    // simplifiedLayout, we cache the value in m_overflow.
+    LayoutUnit oldClientAfterEdge = hasRenderOverflow() ? m_overflow->layoutClientAfterEdge() : clientLogicalBottom();
+    computeOverflow(oldClientAfterEdge, true);
 
-    // If we don't have a parent, we can't be moved into our sibling block.
-    if (!parent())
-        return false;
+    statePusher.pop();
+    
+    updateLayerTransform();
 
-    // An intruded run-in needs to be an inline.
-    if (!runIn->isRenderInline())
-        return false;
+    updateScrollInfoAfterLayout();
 
+    clearNeedsLayout();
     return true;
 }
 
-void RenderBlock::moveRunInToOriginalPosition(RenderObject* runIn)
+void RenderBlock::markFixedPositionObjectForLayoutIfNeeded(RenderObject& child)
 {
-    ASSERT(runIn->isRunIn());
-
-    if (!runInIsPlacedIntoSiblingBlock(runIn))
+    if (child.style().position() != FixedPosition)
         return;
 
-    // FIXME: Run-in that are now placed in sibling block can break up into continuation
-    // chains when new children are added to it. We cannot easily send them back to their
-    // original place since that requires writing integration logic with RenderInline::addChild
-    // and all other places that might cause continuations to be created (without blowing away
-    // |this|). Disabling this feature for now to prevent crashes.
-    if (runIn->isElementContinuation() || runIn->virtualContinuation())
+    bool hasStaticBlockPosition = child.style().hasStaticBlockPosition(isHorizontalWritingMode());
+    bool hasStaticInlinePosition = child.style().hasStaticInlinePosition(isHorizontalWritingMode());
+    if (!hasStaticBlockPosition && !hasStaticInlinePosition)
         return;
 
-    RenderBoxModelObject* oldRunIn = toRenderBoxModelObject(runIn);
-    RenderBoxModelObject* newRunIn = createReplacementRunIn(oldRunIn);
-    destroyRunIn(oldRunIn);
+    auto o = child.parent();
+    while (o && !is<RenderView>(*o) && o->style().position() != AbsolutePosition)
+        o = o->parent();
+    if (o->style().position() != AbsolutePosition)
+        return;
 
-    // Add the run-in block as our previous sibling.
-    parent()->addChild(newRunIn, this);
+    auto& box = downcast<RenderBox>(child);
+    if (hasStaticInlinePosition) {
+        LogicalExtentComputedValues computedValues;
+        box.computeLogicalWidthInRegion(computedValues);
+        LayoutUnit newLeft = computedValues.m_position;
+        if (newLeft != box.logicalLeft())
+            box.setChildNeedsLayout(MarkOnlyThis);
+    } else if (hasStaticBlockPosition) {
+        LayoutUnit oldTop = box.logicalTop();
+        box.updateLogicalHeight();
+        if (box.logicalTop() != oldTop)
+            box.setChildNeedsLayout(MarkOnlyThis);
+    }
+}
 
-    // Make sure that the parent holding the new run-in gets layout.
-    parent()->setNeedsLayoutAndPrefWidthsRecalc();
+LayoutUnit RenderBlock::marginIntrinsicLogicalWidthForChild(RenderBox& child) const
+{
+    // A margin has three types: fixed, percentage, and auto (variable).
+    // Auto and percentage margins become 0 when computing min/max width.
+    // Fixed margins can be added in as is.
+    Length marginLeft = child.style().marginStartUsing(&style());
+    Length marginRight = child.style().marginEndUsing(&style());
+    LayoutUnit margin = 0;
+    if (marginLeft.isFixed())
+        margin += marginLeft.value();
+    if (marginRight.isFixed())
+        margin += marginRight.value();
+    return margin;
 }
 
-LayoutUnit RenderBlock::collapseMargins(RenderBox* child, MarginInfo& marginInfo)
+void RenderBlock::layoutPositionedObject(RenderBox& r, bool relayoutChildren, bool fixedPositionObjectsOnly)
 {
-    bool childDiscardMarginBefore = mustDiscardMarginBeforeForChild(child);
-    bool childDiscardMarginAfter = mustDiscardMarginAfterForChild(child);
-    bool childIsSelfCollapsing = child->isSelfCollapsingBlock();
+    estimateRegionRangeForBoxChild(r);
 
-    // The child discards the before margin when the the after margin has discard in the case of a self collapsing block.
-    childDiscardMarginBefore = childDiscardMarginBefore || (childDiscardMarginAfter && childIsSelfCollapsing);
-
-    // Get the four margin values for the child and cache them.
-    const MarginValues childMargins = marginValuesForChild(child);
-
-    // Get our max pos and neg top margins.
-    LayoutUnit posTop = childMargins.positiveMarginBefore();
-    LayoutUnit negTop = childMargins.negativeMarginBefore();
-
-    // For self-collapsing blocks, collapse our bottom margins into our
-    // top to get new posTop and negTop values.
-    if (childIsSelfCollapsing) {
-        posTop = max(posTop, childMargins.positiveMarginAfter());
-        negTop = max(negTop, childMargins.negativeMarginAfter());
-    }
-    
-    // See if the top margin is quirky. We only care if this child has
-    // margins that will collapse with us.
-    bool topQuirk = hasMarginBeforeQuirk(child);
-
-    if (marginInfo.canCollapseWithMarginBefore()) {
-        if (!childDiscardMarginBefore && !marginInfo.discardMargin()) {
-            // This child is collapsing with the top of the
-            // block. If it has larger margin values, then we need to update
-            // our own maximal values.
-            if (!document()->inQuirksMode() || !marginInfo.quirkContainer() || !topQuirk)
-                setMaxMarginBeforeValues(max(posTop, maxPositiveMarginBefore()), max(negTop, maxNegativeMarginBefore()));
-
-            // The minute any of the margins involved isn't a quirk, don't
-            // collapse it away, even if the margin is smaller (www.webreference.com
-            // has an example of this, a <dt> with 0.8em author-specified inside
-            // a <dl> inside a <td>.
-            if (!marginInfo.determinedMarginBeforeQuirk() && !topQuirk && (posTop - negTop)) {
-                setHasMarginBeforeQuirk(false);
-                marginInfo.setDeterminedMarginBeforeQuirk(true);
-            }
-
-            if (!marginInfo.determinedMarginBeforeQuirk() && topQuirk && !marginBefore())
-                // We have no top margin and our top child has a quirky margin.
-                // We will pick up this quirky margin and pass it through.
-                // This deals with the <td><div><p> case.
-                // Don't do this for a block that split two inlines though. You do
-                // still apply margins in this case.
-                setHasMarginBeforeQuirk(true);
-        } else
-            // The before margin of the container will also discard all the margins it is collapsing with.
-            setMustDiscardMarginBefore();
-    }
-
-    // Once we find a child with discardMarginBefore all the margins collapsing with us must also discard. 
-    if (childDiscardMarginBefore) {
-        marginInfo.setDiscardMargin(true);
-        marginInfo.clearMargin();
+    // A fixed position element with an absolute positioned ancestor has no way of knowing if the latter has changed position. So
+    // if this is a fixed position element, mark it for layout if it has an abspos ancestor and needs to move with that ancestor, i.e. 
+    // it has static position.
+    markFixedPositionObjectForLayoutIfNeeded(r);
+    if (fixedPositionObjectsOnly) {
+        r.layoutIfNeeded();
+        return;
     }
 
-    if (marginInfo.quirkContainer() && marginInfo.atBeforeSideOfBlock() && (posTop - negTop))
-        marginInfo.setHasMarginBeforeQuirk(topQuirk);
-
-    LayoutUnit beforeCollapseLogicalTop = logicalHeight();
-    LayoutUnit logicalTop = beforeCollapseLogicalTop;
-    if (childIsSelfCollapsing) {
-        // For a self collapsing block both the before and after margins get discarded. The block doesn't contribute anything to the height of the block.
-        // Also, the child's top position equals the logical height of the container.
-        if (!childDiscardMarginBefore && !marginInfo.discardMargin()) {
-            // This child has no height. We need to compute our
-            // position before we collapse the child's margins together,
-            // so that we can get an accurate position for the zero-height block.
-            LayoutUnit collapsedBeforePos = max(marginInfo.positiveMargin(), childMargins.positiveMarginBefore());
-            LayoutUnit collapsedBeforeNeg = max(marginInfo.negativeMargin(), childMargins.negativeMarginBefore());
-            marginInfo.setMargin(collapsedBeforePos, collapsedBeforeNeg);
-            
-            // Now collapse the child's margins together, which means examining our
-            // bottom margin values as well. 
-            marginInfo.setPositiveMarginIfLarger(childMargins.positiveMarginAfter());
-            marginInfo.setNegativeMarginIfLarger(childMargins.negativeMarginAfter());
-
-            if (!marginInfo.canCollapseWithMarginBefore())
-                // We need to make sure that the position of the self-collapsing block
-                // is correct, since it could have overflowing content
-                // that needs to be positioned correctly (e.g., a block that
-                // had a specified height of 0 but that actually had subcontent).
-                logicalTop = logicalHeight() + collapsedBeforePos - collapsedBeforeNeg;
-        }
-    } else {
-        if (mustSeparateMarginBeforeForChild(child)) {
-            ASSERT(!marginInfo.discardMargin() || (marginInfo.discardMargin() && !marginInfo.margin()));
-            // If we are at the before side of the block and we collapse, ignore the computed margin
-            // and just add the child margin to the container height. This will correctly position
-            // the child inside the container.
-            LayoutUnit separateMargin = !marginInfo.canCollapseWithMarginBefore() ? marginInfo.margin() : LayoutUnit(0);
-            setLogicalHeight(logicalHeight() + separateMargin + marginBeforeForChild(child));
-            logicalTop = logicalHeight();
-        } else if (!marginInfo.discardMargin() && (!marginInfo.atBeforeSideOfBlock()
-            || (!marginInfo.canCollapseMarginBeforeWithChildren()
-            && (!document()->inQuirksMode() || !marginInfo.quirkContainer() || !marginInfo.hasMarginBeforeQuirk())))) {
-            // We're collapsing with a previous sibling's margins and not
-            // with the top of the block.
-            setLogicalHeight(logicalHeight() + max(marginInfo.positiveMargin(), posTop) - max(marginInfo.negativeMargin(), negTop));
-            logicalTop = logicalHeight();
-        }
-
-        marginInfo.setDiscardMargin(childDiscardMarginAfter);
+    // When a non-positioned block element moves, it may have positioned children that are implicitly positioned relative to the
+    // non-positioned block.  Rather than trying to detect all of these movement cases, we just always lay out positioned
+    // objects that are positioned implicitly like this.  Such objects are rare, and so in typical DHTML menu usage (where everything is
+    // positioned explicitly) this should not incur a performance penalty.
+    if (relayoutChildren || (r.style().hasStaticBlockPosition(isHorizontalWritingMode()) && r.parent() != this))
+        r.setChildNeedsLayout(MarkOnlyThis);
         
-        if (!marginInfo.discardMargin()) {
-            marginInfo.setPositiveMargin(childMargins.positiveMarginAfter());
-            marginInfo.setNegativeMargin(childMargins.negativeMarginAfter());
-        } else
-            marginInfo.clearMargin();
-
-        if (marginInfo.margin())
-            marginInfo.setHasMarginAfterQuirk(hasMarginAfterQuirk(child));
-    }
+    // If relayoutChildren is set and the child has percentage padding or an embedded content box, we also need to invalidate the childs pref widths.
+    if (relayoutChildren && r.needsPreferredWidthsRecalculation())
+        r.setPreferredLogicalWidthsDirty(true, MarkOnlyThis);
     
-    // If margins would pull us past the top of the next page, then we need to pull back and pretend like the margins
-    // collapsed into the page edge.
-    LayoutState* layoutState = view()->layoutState();
-    if (layoutState->isPaginated() && layoutState->pageLogicalHeight() && logicalTop > beforeCollapseLogicalTop
-        && hasNextPage(beforeCollapseLogicalTop)) {
-        LayoutUnit oldLogicalTop = logicalTop;
-        logicalTop = min(logicalTop, nextPageLogicalTop(beforeCollapseLogicalTop));
-        setLogicalHeight(logicalHeight() + (logicalTop - oldLogicalTop));
-    }
-
-    // If we have collapsed into a previous sibling and so reduced the height of the parent, ensure any floats that now
-    // overhang from the previous sibling are added to our parent. If the child's previous sibling itself is a float the child will avoid
-    // or clear it anyway, so don't worry about any floating children it may contain.
-    LayoutUnit oldLogicalHeight = logicalHeight();
-    setLogicalHeight(logicalTop);
-    RenderObject* prev = child->previousSibling();
-    if (prev && prev->isBlockFlow() && !prev->isFloatingOrOutOfFlowPositioned()) {
-        RenderBlock* block = toRenderBlock(prev);
-        if (block->containsFloats() && !block->avoidsFloats() && (block->logicalTop() + block->lowestFloatLogicalBottom()) > logicalTop) 
-            addOverhangingFloats(block, false);
+    r.markForPaginationRelayoutIfNeeded();
+    
+    // We don't have to do a full layout.  We just have to update our position. Try that first. If we have shrink-to-fit width
+    // and we hit the available width constraint, the layoutIfNeeded() will catch it and do a full layout.
+    if (r.needsPositionedMovementLayoutOnly() && r.tryLayoutDoingPositionedMovementOnly())
+        r.clearNeedsLayout();
+        
+    // If we are paginated or in a line grid, compute a vertical position for our object now.
+    // If it's wrong we'll lay out again.
+    LayoutUnit oldLogicalTop = 0;
+    bool needsBlockDirectionLocationSetBeforeLayout = r.needsLayout() && view().layoutState()->needsBlockDirectionLocationSetBeforeLayout();
+    if (needsBlockDirectionLocationSetBeforeLayout) {
+        if (isHorizontalWritingMode() == r.isHorizontalWritingMode())
+            r.updateLogicalHeight();
+        else
+            r.updateLogicalWidth();
+        oldLogicalTop = logicalTopForChild(r);
     }
-    setLogicalHeight(oldLogicalHeight);
-
-    return logicalTop;
-}
-
-LayoutUnit RenderBlock::clearFloatsIfNeeded(RenderBox* child, MarginInfo& marginInfo, LayoutUnit oldTopPosMargin, LayoutUnit oldTopNegMargin, LayoutUnit yPos)
-{
-    LayoutUnit heightIncrease = getClearDelta(child, yPos);
-    if (!heightIncrease)
-        return yPos;
 
-    if (child->isSelfCollapsingBlock()) {
-        bool childDiscardMargin = mustDiscardMarginBeforeForChild(child) || mustDiscardMarginAfterForChild(child);
+    r.layoutIfNeeded();
 
-        // For self-collapsing blocks that clear, they can still collapse their
-        // margins with following siblings.  Reset the current margins to represent
-        // the self-collapsing block's margins only.
-        // If DISCARD is specified for -webkit-margin-collapse, reset the margin values.
-        if (!childDiscardMargin) {
-            MarginValues childMargins = marginValuesForChild(child);
-            marginInfo.setPositiveMargin(max(childMargins.positiveMarginBefore(), childMargins.positiveMarginAfter()));
-            marginInfo.setNegativeMargin(max(childMargins.negativeMarginBefore(), childMargins.negativeMarginAfter()));
-        } else
-            marginInfo.clearMargin();
-        marginInfo.setDiscardMargin(childDiscardMargin);
-
-        // CSS2.1 states:
-        // "If the top and bottom margins of an element with clearance are adjoining, its margins collapse with 
-        // the adjoining margins of following siblings but that resulting margin does not collapse with the bottom margin of the parent block."
-        // So the parent's bottom margin cannot collapse through this block or any subsequent self-collapsing blocks. Check subsequent siblings
-        // for a block with height - if none is found then don't allow the margins to collapse with the parent.
-        bool wouldCollapseMarginsWithParent = marginInfo.canCollapseMarginAfterWithChildren();
-        for (RenderBox* curr = child->nextSiblingBox(); curr && wouldCollapseMarginsWithParent; curr = curr->nextSiblingBox()) {
-            if (!curr->isFloatingOrOutOfFlowPositioned() && !curr->isSelfCollapsingBlock())
-                wouldCollapseMarginsWithParent = false;
-        }
-        if (wouldCollapseMarginsWithParent)
-            marginInfo.setCanCollapseMarginAfterWithChildren(false);
-
-        // CSS2.1: "the amount of clearance is set so that clearance + margin-top = [height of float], i.e., clearance = [height of float] - margin-top"
-        // Move the top of the child box to the bottom of the float ignoring the child's top margin.
-        LayoutUnit collapsedMargin = collapsedMarginBeforeForChild(child);
-        setLogicalHeight(child->logicalTop() - collapsedMargin);
-        // A negative collapsed margin-top value cancels itself out as it has already been factored into |yPos| above.
-        heightIncrease -= max(LayoutUnit(), collapsedMargin);
-    } else
-        // Increase our height by the amount we had to clear.
-        setLogicalHeight(logicalHeight() + heightIncrease);
-    
-    if (marginInfo.canCollapseWithMarginBefore()) {
-        // We can no longer collapse with the top of the block since a clear
-        // occurred.  The empty blocks collapse into the cleared block.
-        // FIXME: This isn't quite correct.  Need clarification for what to do
-        // if the height the cleared block is offset by is smaller than the
-        // margins involved.
-        setMaxMarginBeforeValues(oldTopPosMargin, oldTopNegMargin);
-        marginInfo.setAtBeforeSideOfBlock(false);
-
-        // In case the child discarded the before margin of the block we need to reset the mustDiscardMarginBefore flag to the initial value.
-        setMustDiscardMarginBefore(style()->marginBeforeCollapse() == MDISCARD);
+    // Lay out again if our estimate was wrong.
+    if (needsBlockDirectionLocationSetBeforeLayout && logicalTopForChild(r) != oldLogicalTop) {
+        r.setChildNeedsLayout(MarkOnlyThis);
+        r.layoutIfNeeded();
     }
 
-    LayoutUnit logicalTop = yPos + heightIncrease;
-    // After margin collapsing, one of our floats may now intrude into the child. If the child doesn't contain floats of its own it
-    // won't get picked up for relayout even though the logical top estimate was wrong - so add the newly intruding float now.
-    if (containsFloats() && child->isRenderBlock() && !toRenderBlock(child)->containsFloats() && !child->avoidsFloats() && lowestFloatLogicalBottom() > logicalTop)
-        toRenderBlock(child)->addIntrudingFloats(this, logicalLeftOffsetForContent(), logicalTop);
-
-    return logicalTop;
+    if (updateRegionRangeForBoxChild(r)) {
+        r.setNeedsLayout(MarkOnlyThis);
+        r.layoutIfNeeded();
+    }
 }
 
-void RenderBlock::marginBeforeEstimateForChild(RenderBox* child, LayoutUnit& positiveMarginBefore, LayoutUnit& negativeMarginBefore, bool& discardMarginBefore) const
+void RenderBlock::layoutPositionedObjects(bool relayoutChildren, bool fixedPositionObjectsOnly)
 {
-    // Give up if in quirks mode and we're a body/table cell and the top margin of the child box is quirky.
-    // Give up if the child specified -webkit-margin-collapse: separate that prevents collapsing.
-    // FIXME: Use writing mode independent accessor for marginBeforeCollapse.
-    if ((document()->inQuirksMode() && hasMarginAfterQuirk(child) && (isTableCell() || isBody())) || child->style()->marginBeforeCollapse() == MSEPARATE)
-        return;
-
-    // The margins are discarded by a child that specified -webkit-margin-collapse: discard.
-    // FIXME: Use writing mode independent accessor for marginBeforeCollapse.
-    if (child->style()->marginBeforeCollapse() == MDISCARD) {
-        positiveMarginBefore = 0;
-        negativeMarginBefore = 0;
-        discardMarginBefore = true;
-        return;
-    }
-
-    LayoutUnit beforeChildMargin = marginBeforeForChild(child);
-    positiveMarginBefore = max(positiveMarginBefore, beforeChildMargin);
-    negativeMarginBefore = max(negativeMarginBefore, -beforeChildMargin);
-
-    if (!child->isRenderBlock())
+    TrackedRendererListHashSet* positionedDescendants = positionedObjects();
+    if (!positionedDescendants)
         return;
     
-    RenderBlock* childBlock = toRenderBlock(child);
-    if (childBlock->childrenInline() || childBlock->isWritingModeRoot())
-        return;
-
-    MarginInfo childMarginInfo(childBlock, childBlock->borderAndPaddingBefore(), childBlock->borderAndPaddingAfter());
-    if (!childMarginInfo.canCollapseMarginBeforeWithChildren())
-        return;
+    // Do not cache positionedDescendants->end() in a local variable, since |positionedDescendants| can be mutated
+    // as it is walked. We always need to fetch the new end() value dynamically.
+    for (auto it = positionedDescendants->begin(); it != positionedDescendants->end(); ++it)
+        layoutPositionedObject(**it, relayoutChildren, fixedPositionObjectsOnly);
+}
 
-    RenderBox* grandchildBox = childBlock->firstChildBox();
-    for ( ; grandchildBox; grandchildBox = grandchildBox->nextSiblingBox()) {
-        if (!grandchildBox->isFloatingOrOutOfFlowPositioned())
-            break;
-    }
-    
-    // Give up if there is clearance on the box, since it probably won't collapse into us.
-    if (!grandchildBox || grandchildBox->style()->clear() != CNONE)
+void RenderBlock::markPositionedObjectsForLayout()
+{
+    TrackedRendererListHashSet* positionedDescendants = positionedObjects();
+    if (!positionedDescendants)
         return;
 
-    // Make sure to update the block margins now for the grandchild box so that we're looking at current values.
-    if (grandchildBox->needsLayout()) {
-        grandchildBox->computeAndSetBlockDirectionMargins(this);
-        if (grandchildBox->isRenderBlock()) {
-            RenderBlock* grandchildBlock = toRenderBlock(grandchildBox);
-            grandchildBlock->setHasMarginBeforeQuirk(grandchildBox->style()->hasMarginBeforeQuirk());
-            grandchildBlock->setHasMarginAfterQuirk(grandchildBox->style()->hasMarginAfterQuirk());
-        }
+    for (auto it = positionedDescendants->begin(), end = positionedDescendants->end(); it != end; ++it) {
+        RenderBox* r = *it;
+        r->setChildNeedsLayout();
     }
-
-    // Collapse the margin of the grandchild box with our own to produce an estimate.
-    childBlock->marginBeforeEstimateForChild(grandchildBox, positiveMarginBefore, negativeMarginBefore, discardMarginBefore);
 }
 
-LayoutUnit RenderBlock::estimateLogicalTopPosition(RenderBox* child, const MarginInfo& marginInfo, LayoutUnit& estimateWithoutPagination)
+void RenderBlock::markForPaginationRelayoutIfNeeded()
 {
-    // FIXME: We need to eliminate the estimation of vertical position, because when it's wrong we sometimes trigger a pathological
-    // relayout if there are intruding floats.
-    LayoutUnit logicalTopEstimate = logicalHeight();
-    if (!marginInfo.canCollapseWithMarginBefore()) {
-        LayoutUnit positiveMarginBefore = 0;
-        LayoutUnit negativeMarginBefore = 0;
-        bool discardMarginBefore = false;
-        if (child->selfNeedsLayout()) {
-            // Try to do a basic estimation of how the collapse is going to go.
-            marginBeforeEstimateForChild(child, positiveMarginBefore, negativeMarginBefore, discardMarginBefore);
-        } else {
-            // Use the cached collapsed margin values from a previous layout. Most of the time they
-            // will be right.
-            MarginValues marginValues = marginValuesForChild(child);
-            positiveMarginBefore = max(positiveMarginBefore, marginValues.positiveMarginBefore());
-            negativeMarginBefore = max(negativeMarginBefore, marginValues.negativeMarginBefore());
-            discardMarginBefore = mustDiscardMarginBeforeForChild(child);
-        }
-
-        // Collapse the result with our current margins.
-        if (!discardMarginBefore)
-            logicalTopEstimate += max(marginInfo.positiveMargin(), positiveMarginBefore) - max(marginInfo.negativeMargin(), negativeMarginBefore);
-    }
-
-    // Adjust logicalTopEstimate down to the next page if the margins are so large that we don't fit on the current
-    // page.
-    LayoutState* layoutState = view()->layoutState();
-    if (layoutState->isPaginated() && layoutState->pageLogicalHeight() && logicalTopEstimate > logicalHeight()
-        && hasNextPage(logicalHeight()))
-        logicalTopEstimate = min(logicalTopEstimate, nextPageLogicalTop(logicalHeight()));
-
-    logicalTopEstimate += getClearDelta(child, logicalTopEstimate);
-    
-    estimateWithoutPagination = logicalTopEstimate;
-
-    if (layoutState->isPaginated()) {
-        // If the object has a page or column break value of "before", then we should shift to the top of the next page.
-        logicalTopEstimate = applyBeforeBreak(child, logicalTopEstimate);
-    
-        // For replaced elements and scrolled elements, we want to shift them to the next page if they don't fit on the current one.
-        logicalTopEstimate = adjustForUnsplittableChild(child, logicalTopEstimate);
-        
-        if (!child->selfNeedsLayout() && child->isRenderBlock())
-            logicalTopEstimate += toRenderBlock(child)->paginationStrut();
-    }
+    if (needsLayout() || !view().layoutState()->isPaginated())
+        return;
 
-    return logicalTopEstimate;
+    if (view().layoutState()->pageLogicalHeightChanged() || (view().layoutState()->pageLogicalHeight() && view().layoutState()->pageLogicalOffset(this, logicalTop()) != pageLogicalOffset()))
+        setChildNeedsLayout(MarkOnlyThis);
 }
 
-LayoutUnit RenderBlock::computeStartPositionDeltaForChildAvoidingFloats(const RenderBox* child, LayoutUnit childMarginStart, RenderRegion* region)
+void RenderBlock::paint(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
-    LayoutUnit startPosition = startOffsetForContent(region);
-
-    // Add in our start margin.
-    LayoutUnit oldPosition = startPosition + childMarginStart;
-    LayoutUnit newPosition = oldPosition;
+    RenderNamedFlowFragment* namedFlowFragment = currentRenderNamedFlowFragment();
+    // Check our region range to make sure we need to be painting in this region.
+    if (namedFlowFragment && !namedFlowFragment->flowThread()->objectShouldFragmentInFlowRegion(this, namedFlowFragment))
+        return;
 
-    LayoutUnit blockOffset = logicalTopForChild(child);
-    if (region)
-        blockOffset = max(blockOffset, blockOffset + (region->logicalTopForFlowThreadContent() - offsetFromLogicalTopOfFirstPage()));
+    LayoutPoint adjustedPaintOffset = paintOffset + location();
+    PaintPhase phase = paintInfo.phase;
 
-    LayoutUnit startOff = startOffsetForLine(blockOffset, false, region, logicalHeightForChild(child));
+    // Check if we need to do anything at all.
+    // FIXME: Could eliminate the isDocumentElementRenderer() check if we fix background painting so that the RenderView
+    // paints the root's background.
+    if (!isDocumentElementRenderer()) {
+        LayoutRect overflowBox = overflowRectForPaintRejection(namedFlowFragment);
+        flipForWritingMode(overflowBox);
+        overflowBox.moveBy(adjustedPaintOffset);
+        if (!overflowBox.intersects(paintInfo.rect)
+#if PLATFORM(IOS)
+            // FIXME: This may be applicable to non-iOS ports.
+            && (!hasLayer() || !layer()->isComposited())
+#endif
+        )
+            return;
+    }
 
-    if (style()->textAlign() != WEBKIT_CENTER && !child->style()->marginStartUsing(style()).isAuto()) {
-        if (childMarginStart < 0)
-            startOff += childMarginStart;
-        newPosition = max(newPosition, startOff); // Let the float sit in the child's margin if it can fit.
-    } else if (startOff != startPosition)
-        newPosition = startOff + childMarginStart;
+    bool pushedClip = pushContentsClip(paintInfo, adjustedPaintOffset);
+    paintObject(paintInfo, adjustedPaintOffset);
+    if (pushedClip)
+        popContentsClip(paintInfo, phase, adjustedPaintOffset);
 
-    return newPosition - oldPosition;
+    // Our scrollbar widgets paint exactly when we tell them to, so that they work properly with
+    // z-index. We paint after we painted the background/border, so that the scrollbars will
+    // sit above the background/border.
+    if ((phase == PaintPhaseBlockBackground || phase == PaintPhaseChildBlockBackground) && hasOverflowClip() && layer()
+        && style().visibility() == VISIBLE && paintInfo.shouldPaintWithinRoot(*this) && !paintInfo.paintRootBackgroundOnly())
+        layer()->paintOverflowControls(paintInfo.context(), roundedIntPoint(adjustedPaintOffset), snappedIntRect(paintInfo.rect));
 }
 
-void RenderBlock::determineLogicalLeftPositionForChild(RenderBox* child, ApplyLayoutDeltaMode applyDelta)
+void RenderBlock::paintContents(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
-    LayoutUnit startPosition = borderStart() + paddingStart();
-    if (style()->shouldPlaceBlockDirectionScrollbarOnLogicalLeft())
-        startPosition -= verticalScrollbarWidth();
-    LayoutUnit totalAvailableLogicalWidth = borderAndPaddingLogicalWidth() + availableLogicalWidth();
+    // Avoid painting descendants of the root element when stylesheets haven't loaded.  This eliminates FOUC.
+    // It's ok not to draw, because later on, when all the stylesheets do load, styleResolverChanged() on the Document
+    // will do a full repaint.
+    if (document().didLayoutWithPendingStylesheets() && !isRenderView())
+        return;
 
-    // Add in our start margin.
-    LayoutUnit childMarginStart = marginStartForChild(child);
-    LayoutUnit newPosition = startPosition + childMarginStart;
-        
-    // Some objects (e.g., tables, horizontal rules, overflow:auto blocks) avoid floats.  They need
-    // to shift over as necessary to dodge any floats that might get in the way.
-    if (child->avoidsFloats() && containsFloats() && !flowThreadContainingBlock())
-        newPosition += computeStartPositionDeltaForChildAvoidingFloats(child, marginStartForChild(child));
+    if (childrenInline())
+        paintInlineChildren(paintInfo, paintOffset);
+    else {
+        PaintPhase newPhase = (paintInfo.phase == PaintPhaseChildOutlines) ? PaintPhaseOutline : paintInfo.phase;
+        newPhase = (newPhase == PaintPhaseChildBlockBackgrounds) ? PaintPhaseChildBlockBackground : newPhase;
+
+        // We don't paint our own background, but we do let the kids paint their backgrounds.
+        PaintInfo paintInfoForChild(paintInfo);
+        paintInfoForChild.phase = newPhase;
+        paintInfoForChild.updateSubtreePaintRootForChildren(this);
 
-    setLogicalLeftForChild(child, style()->isLeftToRightDirection() ? newPosition : totalAvailableLogicalWidth - newPosition - logicalWidthForChild(child), applyDelta);
+        // FIXME: Paint-time pagination is obsolete and is now only used by embedded WebViews inside AppKit
+        // NSViews. Do not add any more code for this.
+        bool usePrintRect = !view().printRect().isEmpty();
+        paintChildren(paintInfo, paintOffset, paintInfoForChild, usePrintRect);
+    }
 }
 
-void RenderBlock::setCollapsedBottomMargin(const MarginInfo& marginInfo)
+void RenderBlock::paintChildren(PaintInfo& paintInfo, const LayoutPoint& paintOffset, PaintInfo& paintInfoForChild, bool usePrintRect)
 {
-    if (marginInfo.canCollapseWithMarginAfter() && !marginInfo.canCollapseWithMarginBefore()) {
-        // Update the after side margin of the container to discard if the after margin of the last child also discards and we collapse with it.
-        // Don't update the max margin values because we won't need them anyway.
-        if (marginInfo.discardMargin()) {
-            setMustDiscardMarginAfter();
+    for (auto* child = firstChildBox(); child; child = child->nextSiblingBox()) {
+        if (!paintChild(*child, paintInfo, paintOffset, paintInfoForChild, usePrintRect))
             return;
-        }
-
-        // Update our max pos/neg bottom margins, since we collapsed our bottom margins
-        // with our children.
-        setMaxMarginAfterValues(max(maxPositiveMarginAfter(), marginInfo.positiveMargin()), max(maxNegativeMarginAfter(), marginInfo.negativeMargin()));
-
-        if (!marginInfo.hasMarginAfterQuirk())
-            setHasMarginAfterQuirk(false);
-
-        if (marginInfo.hasMarginAfterQuirk() && !marginAfter())
-            // We have no bottom margin and our last child has a quirky margin.
-            // We will pick up this quirky margin and pass it through.
-            // This deals with the <td><div><p> case.
-            setHasMarginAfterQuirk(true);
     }
 }
 
-void RenderBlock::handleAfterSideOfBlock(LayoutUnit beforeSide, LayoutUnit afterSide, MarginInfo& marginInfo)
+bool RenderBlock::paintChild(RenderBox& child, PaintInfo& paintInfo, const LayoutPoint& paintOffset, PaintInfo& paintInfoForChild, bool usePrintRect, PaintBlockType paintType)
 {
-    marginInfo.setAtAfterSideOfBlock(true);
+    // Check for page-break-before: always, and if it's set, break and bail.
+    bool checkBeforeAlways = !childrenInline() && (usePrintRect && alwaysPageBreak(child.style().breakBefore()));
+    LayoutUnit absoluteChildY = paintOffset.y() + child.y();
+    if (checkBeforeAlways
+        && absoluteChildY > paintInfo.rect.y()
+        && absoluteChildY < paintInfo.rect.maxY()) {
+        view().setBestTruncatedAt(absoluteChildY, this, true);
+        return false;
+    }
 
-    // If we can't collapse with children then go ahead and add in the bottom margin.
-    if (!marginInfo.discardMargin() && (!marginInfo.canCollapseWithMarginAfter() && !marginInfo.canCollapseWithMarginBefore()
-        && (!document()->inQuirksMode() || !marginInfo.quirkContainer() || !marginInfo.hasMarginAfterQuirk())))
-        setLogicalHeight(logicalHeight() + marginInfo.margin());
-        
-    // Now add in our bottom border/padding.
-    setLogicalHeight(logicalHeight() + afterSide);
+    if (!child.isFloating() && child.isReplaced() && usePrintRect && child.height() <= view().printRect().height()) {
+        // Paginate block-level replaced elements.
+        if (absoluteChildY + child.height() > view().printRect().maxY()) {
+            if (absoluteChildY < view().truncatedAt())
+                view().setBestTruncatedAt(absoluteChildY, &child);
+            // If we were able to truncate, don't paint.
+            if (absoluteChildY >= view().truncatedAt())
+                return false;
+        }
+    }
+
+    LayoutPoint childPoint = flipForWritingModeForChild(&child, paintOffset);
+    if (!child.hasSelfPaintingLayer() && !child.isFloating()) {
+        if (paintType == PaintAsInlineBlock)
+            child.paintAsInlineBlock(paintInfoForChild, childPoint);
+        else
+            child.paint(paintInfoForChild, childPoint);
+    }
 
-    // Negative margins can cause our height to shrink below our minimal height (border/padding).
-    // If this happens, ensure that the computed height is increased to the minimal height.
-    setLogicalHeight(max(logicalHeight(), beforeSide + afterSide));
+    // Check for page-break-after: always, and if it's set, break and bail.
+    bool checkAfterAlways = !childrenInline() && (usePrintRect && alwaysPageBreak(child.style().breakAfter()));
+    if (checkAfterAlways
+        && (absoluteChildY + child.height()) > paintInfo.rect.y()
+        && (absoluteChildY + child.height()) < paintInfo.rect.maxY()) {
+        view().setBestTruncatedAt(absoluteChildY + child.height() + std::max<LayoutUnit>(0, child.collapsedMarginAfter()), this, true);
+        return false;
+    }
 
-    // Update our bottom collapsed margin info.
-    setCollapsedBottomMargin(marginInfo);
+    return true;
 }
 
-void RenderBlock::setLogicalLeftForChild(RenderBox* child, LayoutUnit logicalLeft, ApplyLayoutDeltaMode applyDelta)
+void RenderBlock::paintCaret(PaintInfo& paintInfo, const LayoutPoint& paintOffset, CaretType type)
 {
-    if (isHorizontalWritingMode()) {
-        if (applyDelta == ApplyLayoutDelta)
-            view()->addLayoutDelta(LayoutSize(child->x() - logicalLeft, 0));
-        child->setX(logicalLeft);
+    // Paint the caret if the FrameSelection says so or if caret browsing is enabled
+    bool caretBrowsing = frame().settings().caretBrowsingEnabled();
+    RenderBlock* caretPainter;
+    bool isContentEditable;
+    if (type == CursorCaret) {
+        caretPainter = frame().selection().caretRendererWithoutUpdatingLayout();
+        isContentEditable = frame().selection().selection().hasEditableStyle();
     } else {
-        if (applyDelta == ApplyLayoutDelta)
-            view()->addLayoutDelta(LayoutSize(0, child->y() - logicalLeft));
-        child->setY(logicalLeft);
+        caretPainter = frame().page()->dragCaretController().caretRenderer();
+        isContentEditable = frame().page()->dragCaretController().isContentEditable();
     }
-}
 
-void RenderBlock::setLogicalTopForChild(RenderBox* child, LayoutUnit logicalTop, ApplyLayoutDeltaMode applyDelta)
-{
-    if (isHorizontalWritingMode()) {
-        if (applyDelta == ApplyLayoutDelta)
-            view()->addLayoutDelta(LayoutSize(0, child->y() - logicalTop));
-        child->setY(logicalTop);
-    } else {
-        if (applyDelta == ApplyLayoutDelta)
-            view()->addLayoutDelta(LayoutSize(child->x() - logicalTop, 0));
-        child->setX(logicalTop);
+    if (caretPainter == this && (isContentEditable || caretBrowsing)) {
+        if (type == CursorCaret)
+            frame().selection().paintCaret(paintInfo.context(), paintOffset, paintInfo.rect);
+        else
+            frame().page()->dragCaretController().paintDragCaret(&frame(), paintInfo.context(), paintOffset, paintInfo.rect);
     }
 }
 
-void RenderBlock::updateBlockChildDirtyBitsBeforeLayout(bool relayoutChildren, RenderBox* child)
+void RenderBlock::paintObject(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
-    // FIXME: Technically percentage height objects only need a relayout if their percentage isn't going to be turned into
-    // an auto value. Add a method to determine this, so that we can avoid the relayout.
-    if (relayoutChildren || (child->hasRelativeLogicalHeight() && !isRenderView()) || child->hasViewportPercentageLogicalHeight())
-        child->setChildNeedsLayout(true, MarkOnlyThis);
+    PaintPhase paintPhase = paintInfo.phase;
 
-    // If relayoutChildren is set and the child has percentage padding or an embedded content box, we also need to invalidate the childs pref widths.
-    if (relayoutChildren && child->needsPreferredWidthsRecalculation())
-        child->setPreferredLogicalWidthsDirty(true, MarkOnlyThis);
-}
+    // 1. paint background, borders etc
+    if ((paintPhase == PaintPhaseBlockBackground || paintPhase == PaintPhaseChildBlockBackground) && style().visibility() == VISIBLE) {
+        if (hasBoxDecorations()) {
+            bool didClipToRegion = false;
+            
+            RenderNamedFlowFragment* namedFlowFragment = currentRenderNamedFlowFragment();
+            if (namedFlowFragment && is<RenderNamedFlowThread>(paintInfo.paintContainer)) {
+                // If this box goes beyond the current region, then make sure not to overflow the region.
+                // This (overflowing region X altough also fragmented to region X+1) could happen when one of this box's children
+                // overflows region X and is an unsplittable element (like an image).
+                // The same applies for a box overflowing the top of region X when that box is also fragmented in region X-1.
 
-void RenderBlock::dirtyForLayoutFromPercentageHeightDescendants()
-{
-    if (!gPercentHeightDescendantsMap)
-        return;
+                paintInfo.context().save();
+                didClipToRegion = true;
 
-    TrackedRendererListHashSet* descendants = gPercentHeightDescendantsMap->get(this);
-    if (!descendants)
-        return;
-    
-    TrackedRendererListHashSet::iterator end = descendants->end();
-    for (TrackedRendererListHashSet::iterator it = descendants->begin(); it != end; ++it) {
-        RenderBox* box = *it;
-        while (box != this) {
-            if (box->normalChildNeedsLayout())
-                break;
-            box->setChildNeedsLayout(true, MarkOnlyThis);
-            
-            // If the width of an image is affected by the height of a child (e.g., an image with an aspect ratio),
-            // then we have to dirty preferred widths, since even enclosing blocks can become dirty as a result.
-            // (A horizontal flexbox that contains an inline image wrapped in an anonymous block for example.)
-            if (box->hasAspectRatio()) 
-                box->setPreferredLogicalWidthsDirty(true);
+                paintInfo.context().clip(downcast<RenderNamedFlowThread>(*paintInfo.paintContainer).decorationsClipRectForBoxInNamedFlowFragment(*this, *namedFlowFragment));
+            }
+
+            paintBoxDecorations(paintInfo, paintOffset);
             
-            box = box->containingBlock();
-            ASSERT(box);
-            if (!box)
-                break;
+            if (didClipToRegion)
+                paintInfo.context().restore();
         }
     }
-}
 
-void RenderBlock::layoutBlockChildren(bool relayoutChildren, LayoutUnit& maxFloatLogicalBottom)
-{
-    dirtyForLayoutFromPercentageHeightDescendants();
+    if (paintPhase == PaintPhaseMask && style().visibility() == VISIBLE) {
+        paintMask(paintInfo, paintOffset);
+        return;
+    }
 
-    LayoutUnit beforeEdge = borderAndPaddingBefore();
-    LayoutUnit afterEdge = borderAndPaddingAfter() + scrollbarLogicalHeight();
+    if (paintPhase == PaintPhaseClippingMask && style().visibility() == VISIBLE) {
+        paintClippingMask(paintInfo, paintOffset);
+        return;
+    }
 
-    setLogicalHeight(beforeEdge);
-    
-    // Lay out our hypothetical grid line as though it occurs at the top of the block.
-    if (view()->layoutState()->lineGrid() == this)
-        layoutLineGridBox();
+    // If just painting the root background, then return.
+    if (paintInfo.paintRootBackgroundOnly())
+        return;
 
-    // The margin struct caches all our current margin collapsing state.  The compact struct caches state when we encounter compacts,
-    MarginInfo marginInfo(this, beforeEdge, afterEdge);
+    // Adjust our painting position if we're inside a scrolled layer (e.g., an overflow:auto div).
+    LayoutPoint scrolledOffset = paintOffset;
+    scrolledOffset.move(-scrolledContentOffset());
 
-    // Fieldsets need to find their legend and position it inside the border of the object.
-    // The legend then gets skipped during normal layout.  The same is true for ruby text.
-    // It doesn't get included in the normal layout process but is instead skipped.
-    RenderObject* childToExclude = layoutSpecialExcludedChild(relayoutChildren);
+    // Column rules need to account for scrolling and clipping.
+    // FIXME: Clipping of column rules does not work. We will need a separate paint phase for column rules I suspect in order to get
+    // clipping correct (since it has to paint as background but is still considered "contents").
+    if ((paintPhase == PaintPhaseBlockBackground || paintPhase == PaintPhaseChildBlockBackground) && style().visibility() == VISIBLE)
+        paintColumnRules(paintInfo, scrolledOffset);
 
-    LayoutUnit previousFloatLogicalBottom = 0;
-    maxFloatLogicalBottom = 0;
+    // Done with backgrounds, borders and column rules.
+    if (paintPhase == PaintPhaseBlockBackground)
+        return;
+    
+    // 2. paint contents
+    if (paintPhase != PaintPhaseSelfOutline)
+        paintContents(paintInfo, scrolledOffset);
 
-    RenderBox* next = firstChildBox();
+    // 3. paint selection
+    // FIXME: Make this work with multi column layouts.  For now don't fill gaps.
+    bool isPrinting = document().printing();
+    if (!isPrinting)
+        paintSelection(paintInfo, scrolledOffset); // Fill in gaps in selection on lines and between blocks.
 
-    while (next) {
-        RenderBox* child = next;
-        next = child->nextSiblingBox();
+    // 4. paint floats.
+    if (paintPhase == PaintPhaseFloat || paintPhase == PaintPhaseSelection || paintPhase == PaintPhaseTextClip)
+        paintFloats(paintInfo, scrolledOffset, paintPhase == PaintPhaseSelection || paintPhase == PaintPhaseTextClip);
 
-        if (childToExclude == child)
-            continue; // Skip this child, since it will be positioned by the specialized subclass (fieldsets and ruby runs).
+    // 5. paint outline.
+    if ((paintPhase == PaintPhaseOutline || paintPhase == PaintPhaseSelfOutline) && hasOutline() && style().visibility() == VISIBLE)
+        paintOutline(paintInfo, LayoutRect(paintOffset, size()));
 
-        updateBlockChildDirtyBitsBeforeLayout(relayoutChildren, child);
+    // 6. paint continuation outlines.
+    if ((paintPhase == PaintPhaseOutline || paintPhase == PaintPhaseChildOutlines)) {
+        RenderInline* inlineCont = inlineElementContinuation();
+        if (inlineCont && inlineCont->hasOutline() && inlineCont->style().visibility() == VISIBLE) {
+            RenderInline* inlineRenderer = downcast<RenderInline>(inlineCont->element()->renderer());
+            RenderBlock* containingBlock = this->containingBlock();
 
-        if (child->isOutOfFlowPositioned()) {
-            child->containingBlock()->insertPositionedObject(child);
-            adjustPositionedBlock(child, marginInfo);
-            continue;
-        }
-        if (child->isFloating()) {
-            insertFloatingObject(child);
-            adjustFloatingBlock(marginInfo);
-            continue;
+            bool inlineEnclosedInSelfPaintingLayer = false;
+            for (RenderBoxModelObject* box = inlineRenderer; box != containingBlock; box = &box->parent()->enclosingBoxModelObject()) {
+                if (box->hasSelfPaintingLayer()) {
+                    inlineEnclosedInSelfPaintingLayer = true;
+                    break;
+                }
+            }
+
+            // Do not add continuations for outline painting by our containing block if we are a relative positioned
+            // anonymous block (i.e. have our own layer), paint them straightaway instead. This is because a block depends on renderers in its continuation table being
+            // in the same layer. 
+            if (!inlineEnclosedInSelfPaintingLayer && !hasLayer())
+                containingBlock->addContinuationWithOutline(inlineRenderer);
+            else if (!inlineRenderer->firstLineBox() || (!inlineEnclosedInSelfPaintingLayer && hasLayer()))
+                inlineRenderer->paintOutline(paintInfo, paintOffset - locationOffset() + inlineRenderer->containingBlock()->location());
         }
+        paintContinuationOutlines(paintInfo, paintOffset);
+    }
 
-        // Lay out the child.
-        layoutBlockChild(child, marginInfo, previousFloatLogicalBottom, maxFloatLogicalBottom);
+    // 7. paint caret.
+    // If the caret's node's render object's containing block is this block, and the paint action is PaintPhaseForeground,
+    // then paint the caret.
+    if (paintPhase == PaintPhaseForeground) {        
+        paintCaret(paintInfo, paintOffset, CursorCaret);
+        paintCaret(paintInfo, paintOffset, DragCaret);
     }
-    
-    // Now do the handling of the bottom of the block, adding in our bottom border/padding and
-    // determining the correct collapsed bottom margin information.
-    handleAfterSideOfBlock(beforeEdge, afterEdge, marginInfo);
 }
 
-void RenderBlock::layoutBlockChild(RenderBox* child, MarginInfo& marginInfo, LayoutUnit& previousFloatLogicalBottom, LayoutUnit& maxFloatLogicalBottom)
-{
-    LayoutUnit oldPosMarginBefore = maxPositiveMarginBefore();
-    LayoutUnit oldNegMarginBefore = maxNegativeMarginBefore();
-
-    // The child is a normal flow object.  Compute the margins we will use for collapsing now.
-    child->computeAndSetBlockDirectionMargins(this);
-
-    // Try to guess our correct logical top position.  In most cases this guess will
-    // be correct.  Only if we're wrong (when we compute the real logical top position)
-    // will we have to potentially relayout.
-    LayoutUnit estimateWithoutPagination;
-    LayoutUnit logicalTopEstimate = estimateLogicalTopPosition(child, marginInfo, estimateWithoutPagination);
-
-    // Cache our old rect so that we can dirty the proper repaint rects if the child moves.
-    LayoutRect oldRect = child->frameRect();
-    LayoutUnit oldLogicalTop = logicalTopForChild(child);
-
-#if !ASSERT_DISABLED
-    LayoutSize oldLayoutDelta = view()->layoutDelta();
-#endif
-    // Go ahead and position the child as though it didn't collapse with the top.
-    setLogicalTopForChild(child, logicalTopEstimate, ApplyLayoutDelta);
-
-    RenderBlock* childRenderBlock = child->isRenderBlock() ? toRenderBlock(child) : 0;
-    bool markDescendantsWithFloats = false;
-    if (logicalTopEstimate != oldLogicalTop && !child->avoidsFloats() && childRenderBlock && childRenderBlock->containsFloats())
-        markDescendantsWithFloats = true;
-#if ENABLE(SUBPIXEL_LAYOUT)
-    else if (UNLIKELY(logicalTopEstimate.mightBeSaturated()))
-        // logicalTopEstimate, returned by estimateLogicalTopPosition, might be saturated for
-        // very large elements. If it does the comparison with oldLogicalTop might yield a
-        // false negative as adding and removing margins, borders etc from a saturated number
-        // might yield incorrect results. If this is the case always mark for layout.
-        markDescendantsWithFloats = true;
-#endif
-    else if (!child->avoidsFloats() || child->shrinkToAvoidFloats()) {
-        // If an element might be affected by the presence of floats, then always mark it for
-        // layout.
-        LayoutUnit fb = max(previousFloatLogicalBottom, lowestFloatLogicalBottom());
-        if (fb > logicalTopEstimate)
-            markDescendantsWithFloats = true;
-    }
+RenderInline* RenderBlock::inlineElementContinuation() const
+{ 
+    RenderBoxModelObject* continuation = this->continuation();
+    return is<RenderInline>(continuation) ? downcast<RenderInline>(continuation) : nullptr;
+}
 
-    if (childRenderBlock) {
-        if (markDescendantsWithFloats)
-            childRenderBlock->markAllDescendantsWithFloatsForLayout();
-        if (!child->isWritingModeRoot())
-            previousFloatLogicalBottom = max(previousFloatLogicalBottom, oldLogicalTop + childRenderBlock->lowestFloatLogicalBottom());
-    }
-
-    if (!child->needsLayout())
-        child->markForPaginationRelayoutIfNeeded();
-
-    bool childHadLayout = child->everHadLayout();
-    bool childNeededLayout = child->needsLayout();
-    if (childNeededLayout)
-        child->layout();
-
-    // Cache if we are at the top of the block right now.
-    bool atBeforeSideOfBlock = marginInfo.atBeforeSideOfBlock();
-
-    // Now determine the correct ypos based off examination of collapsing margin
-    // values.
-    LayoutUnit logicalTopBeforeClear = collapseMargins(child, marginInfo);
-
-    // Now check for clear.
-    LayoutUnit logicalTopAfterClear = clearFloatsIfNeeded(child, marginInfo, oldPosMarginBefore, oldNegMarginBefore, logicalTopBeforeClear);
-    
-    bool paginated = view()->layoutState()->isPaginated();
-    if (paginated)
-        logicalTopAfterClear = adjustBlockChildForPagination(logicalTopAfterClear, estimateWithoutPagination, child,
-            atBeforeSideOfBlock && logicalTopBeforeClear == logicalTopAfterClear);
-
-    setLogicalTopForChild(child, logicalTopAfterClear, ApplyLayoutDelta);
-
-    // Now we have a final top position.  See if it really does end up being different from our estimate.
-    // clearFloatsIfNeeded can also mark the child as needing a layout even though we didn't move. This happens
-    // when collapseMargins dynamically adds overhanging floats because of a child with negative margins.
-    if (logicalTopAfterClear != logicalTopEstimate || child->needsLayout() || (paginated && childRenderBlock && childRenderBlock->shouldBreakAtLineToAvoidWidow())) {
-        if (child->shrinkToAvoidFloats()) {
-            // The child's width depends on the line width.
-            // When the child shifts to clear an item, its width can
-            // change (because it has more available line width).
-            // So go ahead and mark the item as dirty.
-            child->setChildNeedsLayout(true, MarkOnlyThis);
-        }
-        
-        if (childRenderBlock) {
-            if (!child->avoidsFloats() && childRenderBlock->containsFloats())
-                childRenderBlock->markAllDescendantsWithFloatsForLayout();
-            if (!child->needsLayout())
-                child->markForPaginationRelayoutIfNeeded();
-        }
-
-        // Our guess was wrong. Make the child lay itself out again.
-        child->layoutIfNeeded();
-    }
-
-    // We are no longer at the top of the block if we encounter a non-empty child.  
-    // This has to be done after checking for clear, so that margins can be reset if a clear occurred.
-    if (marginInfo.atBeforeSideOfBlock() && !child->isSelfCollapsingBlock())
-        marginInfo.setAtBeforeSideOfBlock(false);
-
-    // Now place the child in the correct left position
-    determineLogicalLeftPositionForChild(child, ApplyLayoutDelta);
-
-    // Update our height now that the child has been placed in the correct position.
-    setLogicalHeight(logicalHeight() + logicalHeightForChild(child));
-    if (mustSeparateMarginAfterForChild(child)) {
-        setLogicalHeight(logicalHeight() + marginAfterForChild(child));
-        marginInfo.clearMargin();
-    }
-    // If the child has overhanging floats that intrude into following siblings (or possibly out
-    // of this block), then the parent gets notified of the floats now.
-    if (childRenderBlock && childRenderBlock->containsFloats())
-        maxFloatLogicalBottom = max(maxFloatLogicalBottom, addOverhangingFloats(toRenderBlock(child), !childNeededLayout));
-
-    LayoutSize childOffset = child->location() - oldRect.location();
-    if (childOffset.width() || childOffset.height()) {
-        view()->addLayoutDelta(childOffset);
-
-        // If the child moved, we have to repaint it as well as any floating/positioned
-        // descendants.  An exception is if we need a layout.  In this case, we know we're going to
-        // repaint ourselves (and the child) anyway.
-        if (childHadLayout && !selfNeedsLayout() && child->checkForRepaintDuringLayout())
-            child->repaintDuringLayoutIfMoved(oldRect);
-    }
-
-    if (!childHadLayout && child->checkForRepaintDuringLayout()) {
-        child->repaint();
-        child->repaintOverhangingFloats(true);
-    }
-
-    if (paginated) {
-        // Check for an after page/column break.
-        LayoutUnit newHeight = applyAfterBreak(child, logicalHeight(), marginInfo);
-        if (newHeight != height())
-            setLogicalHeight(newHeight);
-    }
-
-    ASSERT(view()->layoutDeltaMatches(oldLayoutDelta));
-}
-
-void RenderBlock::simplifiedNormalFlowLayout()
-{
-    if (childrenInline()) {
-        ListHashSet<RootInlineBox*> lineBoxes;
-        for (InlineWalker walker(this); !walker.atEnd(); walker.advance()) {
-            RenderObject* o = walker.current();
-            if (!o->isOutOfFlowPositioned() && (o->isReplaced() || o->isFloating())) {
-                o->layoutIfNeeded();
-                if (toRenderBox(o)->inlineBoxWrapper()) {
-                    RootInlineBox* box = toRenderBox(o)->inlineBoxWrapper()->root();
-                    lineBoxes.add(box);
-                }
-            } else if (o->isText() || (o->isRenderInline() && !walker.atEndOfInline()))
-                o->setNeedsLayout(false);
-        }
-
-        // FIXME: Glyph overflow will get lost in this case, but not really a big deal.
-        GlyphOverflowAndFallbackFontsMap textBoxDataMap;                  
-        for (ListHashSet<RootInlineBox*>::const_iterator it = lineBoxes.begin(); it != lineBoxes.end(); ++it) {
-            RootInlineBox* box = *it;
-            box->computeOverflow(box->lineTop(), box->lineBottom(), textBoxDataMap);
-        }
-    } else {
-        for (RenderBox* box = firstChildBox(); box; box = box->nextSiblingBox()) {
-            if (!box->isOutOfFlowPositioned())
-                box->layoutIfNeeded();
-        }
-    }
-}
-
-bool RenderBlock::simplifiedLayout()
-{
-    if ((!posChildNeedsLayout() && !needsSimplifiedNormalFlowLayout()) || normalChildNeedsLayout() || selfNeedsLayout())
-        return false;
-
-    LayoutStateMaintainer statePusher(view(), this, locationOffset(), hasColumns() || hasTransform() || hasReflection() || style()->isFlippedBlocksWritingMode());
-    
-    if (needsPositionedMovementLayout() && !tryLayoutDoingPositionedMovementOnly())
-        return false;
-
-    // Lay out positioned descendants or objects that just need to recompute overflow.
-    if (needsSimplifiedNormalFlowLayout())
-        simplifiedNormalFlowLayout();
-
-    // Lay out our positioned objects if our positioned child bit is set.
-    // Also, if an absolute position element inside a relative positioned container moves, and the absolute element has a fixed position
-    // child, neither the fixed element nor its container learn of the movement since posChildNeedsLayout() is only marked as far as the 
-    // relative positioned container. So if we can have fixed pos objects in our positioned objects list check if any of them
-    // are statically positioned and thus need to move with their absolute ancestors.
-    bool canContainFixedPosObjects = canContainFixedPositionObjects();
-    if (posChildNeedsLayout() || canContainFixedPosObjects)
-        layoutPositionedObjects(false, !posChildNeedsLayout() && canContainFixedPosObjects);
-
-    // Recompute our overflow information.
-    // FIXME: We could do better here by computing a temporary overflow object from layoutPositionedObjects and only
-    // updating our overflow if we either used to have overflow or if the new temporary object has overflow.
-    // For now just always recompute overflow.  This is no worse performance-wise than the old code that called rightmostPosition and
-    // lowestPosition on every relayout so it's not a regression.
-    // computeOverflow expects the bottom edge before we clamp our height. Since this information isn't available during
-    // simplifiedLayout, we cache the value in m_overflow.
-    LayoutUnit oldClientAfterEdge = hasRenderOverflow() ? m_overflow->layoutClientAfterEdge() : clientLogicalBottom();
-    computeOverflow(oldClientAfterEdge, true);
-
-    statePusher.pop();
-    
-    updateLayerTransform();
-
-    updateScrollInfoAfterLayout();
-
-    setNeedsLayout(false);
-    return true;
-}
-
-void RenderBlock::markFixedPositionObjectForLayoutIfNeeded(RenderObject* child)
-{
-    if (child->style()->position() != FixedPosition)
-        return;
-
-    bool hasStaticBlockPosition = child->style()->hasStaticBlockPosition(isHorizontalWritingMode());
-    bool hasStaticInlinePosition = child->style()->hasStaticInlinePosition(isHorizontalWritingMode());
-    if (!hasStaticBlockPosition && !hasStaticInlinePosition)
-        return;
-
-    RenderObject* o = child->parent();
-    while (o && !o->isRenderView() && o->style()->position() != AbsolutePosition)
-        o = o->parent();
-    if (o->style()->position() != AbsolutePosition)
-        return;
-
-    RenderBox* box = toRenderBox(child);
-    if (hasStaticInlinePosition) {
-        LogicalExtentComputedValues computedValues;
-        box->computeLogicalWidthInRegion(computedValues);
-        LayoutUnit newLeft = computedValues.m_position;
-        if (newLeft != box->logicalLeft())
-            child->setChildNeedsLayout(true, MarkOnlyThis);
-    } else if (hasStaticBlockPosition) {
-        LayoutUnit oldTop = box->logicalTop();
-        box->updateLogicalHeight();
-        if (box->logicalTop() != oldTop)
-            child->setChildNeedsLayout(true, MarkOnlyThis);
-    }
-}
-
-void RenderBlock::layoutPositionedObjects(bool relayoutChildren, bool fixedPositionObjectsOnly)
-{
-    TrackedRendererListHashSet* positionedDescendants = positionedObjects();
-    if (!positionedDescendants)
-        return;
-        
-    if (hasColumns())
-        view()->layoutState()->clearPaginationInformation(); // Positioned objects are not part of the column flow, so they don't paginate with the columns.
-
-    RenderBox* r;
-    TrackedRendererListHashSet::iterator end = positionedDescendants->end();
-    for (TrackedRendererListHashSet::iterator it = positionedDescendants->begin(); it != end; ++it) {
-        r = *it;
-
-        // A fixed position element with an absolute positioned ancestor has no way of knowing if the latter has changed position. So
-        // if this is a fixed position element, mark it for layout if it has an abspos ancestor and needs to move with that ancestor, i.e. 
-        // it has static position.
-        markFixedPositionObjectForLayoutIfNeeded(r);
-        if (fixedPositionObjectsOnly) {
-            r->layoutIfNeeded();
-            continue;
-        }
-
-        // When a non-positioned block element moves, it may have positioned children that are implicitly positioned relative to the
-        // non-positioned block.  Rather than trying to detect all of these movement cases, we just always lay out positioned
-        // objects that are positioned implicitly like this.  Such objects are rare, and so in typical DHTML menu usage (where everything is
-        // positioned explicitly) this should not incur a performance penalty.
-        if (relayoutChildren || (r->style()->hasStaticBlockPosition(isHorizontalWritingMode()) && r->parent() != this))
-            r->setChildNeedsLayout(true, MarkOnlyThis);
-            
-        // If relayoutChildren is set and the child has percentage padding or an embedded content box, we also need to invalidate the childs pref widths.
-        if (relayoutChildren && r->needsPreferredWidthsRecalculation())
-            r->setPreferredLogicalWidthsDirty(true, MarkOnlyThis);
-        
-        if (!r->needsLayout())
-            r->markForPaginationRelayoutIfNeeded();
-        
-        // We don't have to do a full layout.  We just have to update our position. Try that first. If we have shrink-to-fit width
-        // and we hit the available width constraint, the layoutIfNeeded() will catch it and do a full layout.
-        if (r->needsPositionedMovementLayoutOnly() && r->tryLayoutDoingPositionedMovementOnly())
-            r->setNeedsLayout(false);
-            
-        // If we are paginated or in a line grid, go ahead and compute a vertical position for our object now.
-        // If it's wrong we'll lay out again.
-        LayoutUnit oldLogicalTop = 0;
-        bool needsBlockDirectionLocationSetBeforeLayout = r->needsLayout() && view()->layoutState()->needsBlockDirectionLocationSetBeforeLayout(); 
-        if (needsBlockDirectionLocationSetBeforeLayout) {
-            if (isHorizontalWritingMode() == r->isHorizontalWritingMode())
-                r->updateLogicalHeight();
-            else
-                r->updateLogicalWidth();
-            oldLogicalTop = logicalTopForChild(r);
-        }
-        
-        r->layoutIfNeeded();
-
-        // Lay out again if our estimate was wrong.
-        if (needsBlockDirectionLocationSetBeforeLayout && logicalTopForChild(r) != oldLogicalTop) {
-            r->setChildNeedsLayout(true, MarkOnlyThis);
-            r->layoutIfNeeded();
-        }
-    }
-    
-    if (hasColumns())
-        view()->layoutState()->m_columnInfo = columnInfo(); // FIXME: Kind of gross. We just put this back into the layout state so that pop() will work.
-}
-
-void RenderBlock::markPositionedObjectsForLayout()
-{
-    TrackedRendererListHashSet* positionedDescendants = positionedObjects();
-    if (positionedDescendants) {
-        RenderBox* r;
-        TrackedRendererListHashSet::iterator end = positionedDescendants->end();
-        for (TrackedRendererListHashSet::iterator it = positionedDescendants->begin(); it != end; ++it) {
-            r = *it;
-            r->setChildNeedsLayout(true);
-        }
-    }
-}
-
-void RenderBlock::markForPaginationRelayoutIfNeeded()
-{
-    ASSERT(!needsLayout());
-    if (needsLayout())
-        return;
-
-    if (view()->layoutState()->pageLogicalHeightChanged() || (view()->layoutState()->pageLogicalHeight() && view()->layoutState()->pageLogicalOffset(this, logicalTop()) != pageLogicalOffset()) || shouldBreakAtLineToAvoidWidow())
-        setChildNeedsLayout(true, MarkOnlyThis);
-}
-
-void RenderBlock::repaintOverhangingFloats(bool paintAllDescendants)
-{
-    // Repaint any overhanging floats (if we know we're the one to paint them).
-    // Otherwise, bail out.
-    if (!hasOverhangingFloats())
-        return;
-
-    // FIXME: Avoid disabling LayoutState. At the very least, don't disable it for floats originating
-    // in this block. Better yet would be to push extra state for the containers of other floats.
-    LayoutStateDisabler layoutStateDisabler(view());
-    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    FloatingObjectSetIterator end = floatingObjectSet.end();
-    for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-        FloatingObject* r = *it;
-        // Only repaint the object if it is overhanging, is not in its own layer, and
-        // is our responsibility to paint (m_shouldPaint is set). When paintAllDescendants is true, the latter
-        // condition is replaced with being a descendant of us.
-        if (logicalBottomForFloat(r) > logicalHeight() && ((paintAllDescendants && r->m_renderer->isDescendantOf(this)) || r->shouldPaint()) && !r->m_renderer->hasSelfPaintingLayer()) {
-            r->m_renderer->repaint();
-            r->m_renderer->repaintOverhangingFloats(false);
-        }
-    }
-}
- 
-void RenderBlock::paint(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
-{
-    LayoutPoint adjustedPaintOffset = paintOffset + location();
-    
-    PaintPhase phase = paintInfo.phase;
-
-    // Check if we need to do anything at all.
-    // FIXME: Could eliminate the isRoot() check if we fix background painting so that the RenderView
-    // paints the root's background.
-    if (!isRoot()) {
-        LayoutRect overflowBox = overflowRectForPaintRejection();
-        flipForWritingMode(overflowBox);
-        overflowBox.inflate(maximalOutlineSize(paintInfo.phase));
-        overflowBox.moveBy(adjustedPaintOffset);
-        if (!overflowBox.intersects(paintInfo.rect))
-            return;
-    }
-
-    bool pushedClip = pushContentsClip(paintInfo, adjustedPaintOffset);
-    paintObject(paintInfo, adjustedPaintOffset);
-    if (pushedClip)
-        popContentsClip(paintInfo, phase, adjustedPaintOffset);
-
-    // Our scrollbar widgets paint exactly when we tell them to, so that they work properly with
-    // z-index.  We paint after we painted the background/border, so that the scrollbars will
-    // sit above the background/border.
-    if (hasOverflowClip() && style()->visibility() == VISIBLE && (phase == PaintPhaseBlockBackground || phase == PaintPhaseChildBlockBackground) && paintInfo.shouldPaintWithinRoot(this) && !paintInfo.paintRootBackgroundOnly())
-        layer()->paintOverflowControls(paintInfo.context, roundedIntPoint(adjustedPaintOffset), paintInfo.rect);
-}
-
-void RenderBlock::paintColumnRules(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
-{
-    if (paintInfo.context->paintingDisabled())
-        return;
-
-    const Color& ruleColor = style()->visitedDependentColor(CSSPropertyWebkitColumnRuleColor);
-    bool ruleTransparent = style()->columnRuleIsTransparent();
-    EBorderStyle ruleStyle = style()->columnRuleStyle();
-    LayoutUnit ruleThickness = style()->columnRuleWidth();
-    LayoutUnit colGap = columnGap();
-    bool renderRule = ruleStyle > BHIDDEN && !ruleTransparent;
-    if (!renderRule)
-        return;
-
-    ColumnInfo* colInfo = columnInfo();
-    unsigned colCount = columnCount(colInfo);
-
-    bool antialias = shouldAntialiasLines(paintInfo.context);
-
-    if (colInfo->progressionAxis() == ColumnInfo::InlineAxis) {
-        bool leftToRight = style()->isLeftToRightDirection() ^ colInfo->progressionIsReversed();
-        LayoutUnit currLogicalLeftOffset = leftToRight ? LayoutUnit() : contentLogicalWidth();
-        LayoutUnit ruleAdd = logicalLeftOffsetForContent();
-        LayoutUnit ruleLogicalLeft = leftToRight ? LayoutUnit() : contentLogicalWidth();
-        LayoutUnit inlineDirectionSize = colInfo->desiredColumnWidth();
-        BoxSide boxSide = isHorizontalWritingMode()
-            ? leftToRight ? BSLeft : BSRight
-            : leftToRight ? BSTop : BSBottom;
-
-        for (unsigned i = 0; i < colCount; i++) {
-            // Move to the next position.
-            if (leftToRight) {
-                ruleLogicalLeft += inlineDirectionSize + colGap / 2;
-                currLogicalLeftOffset += inlineDirectionSize + colGap;
-            } else {
-                ruleLogicalLeft -= (inlineDirectionSize + colGap / 2);
-                currLogicalLeftOffset -= (inlineDirectionSize + colGap);
-            }
-           
-            // Now paint the column rule.
-            if (i < colCount - 1) {
-                LayoutUnit ruleLeft = isHorizontalWritingMode() ? paintOffset.x() + ruleLogicalLeft - ruleThickness / 2 + ruleAdd : paintOffset.x() + borderLeft() + paddingLeft();
-                LayoutUnit ruleRight = isHorizontalWritingMode() ? ruleLeft + ruleThickness : ruleLeft + contentWidth();
-                LayoutUnit ruleTop = isHorizontalWritingMode() ? paintOffset.y() + borderTop() + paddingTop() : paintOffset.y() + ruleLogicalLeft - ruleThickness / 2 + ruleAdd;
-                LayoutUnit ruleBottom = isHorizontalWritingMode() ? ruleTop + contentHeight() : ruleTop + ruleThickness;
-                IntRect pixelSnappedRuleRect = pixelSnappedIntRectFromEdges(ruleLeft, ruleTop, ruleRight, ruleBottom);
-                drawLineForBoxSide(paintInfo.context, pixelSnappedRuleRect.x(), pixelSnappedRuleRect.y(), pixelSnappedRuleRect.maxX(), pixelSnappedRuleRect.maxY(), boxSide, ruleColor, ruleStyle, 0, 0, antialias);
-            }
-            
-            ruleLogicalLeft = currLogicalLeftOffset;
-        }
-    } else {
-        bool topToBottom = !style()->isFlippedBlocksWritingMode() ^ colInfo->progressionIsReversed();
-        LayoutUnit ruleLeft = isHorizontalWritingMode()
-            ? borderLeft() + paddingLeft()
-            : colGap / 2 - colGap - ruleThickness / 2 + (!colInfo->progressionIsReversed() ? borderAndPaddingBefore() : borderAndPaddingAfter());
-        LayoutUnit ruleWidth = isHorizontalWritingMode() ? contentWidth() : ruleThickness;
-        LayoutUnit ruleTop = isHorizontalWritingMode()
-            ? colGap / 2 - colGap - ruleThickness / 2 + (!colInfo->progressionIsReversed() ? borderAndPaddingBefore() : borderAndPaddingAfter())
-            : borderStart() + paddingStart();
-        LayoutUnit ruleHeight = isHorizontalWritingMode() ? ruleThickness : contentHeight();
-        LayoutRect ruleRect(ruleLeft, ruleTop, ruleWidth, ruleHeight);
-
-        if (!topToBottom) {
-            if (isHorizontalWritingMode())
-                ruleRect.setY(height() - ruleRect.maxY());
-            else
-                ruleRect.setX(width() - ruleRect.maxX());
-        }
-
-        ruleRect.moveBy(paintOffset);
-
-        BoxSide boxSide = isHorizontalWritingMode()
-            ? topToBottom ? BSTop : BSBottom
-            : topToBottom ? BSLeft : BSRight;
-
-        LayoutSize step(0, topToBottom ? colInfo->columnHeight() + colGap : -(colInfo->columnHeight() + colGap));
-        if (!isHorizontalWritingMode())
-            step = step.transposedSize();
-
-        for (unsigned i = 1; i < colCount; i++) {
-            ruleRect.move(step);
-            IntRect pixelSnappedRuleRect = pixelSnappedIntRect(ruleRect);
-            drawLineForBoxSide(paintInfo.context, pixelSnappedRuleRect.x(), pixelSnappedRuleRect.y(), pixelSnappedRuleRect.maxX(), pixelSnappedRuleRect.maxY(), boxSide, ruleColor, ruleStyle, 0, 0, antialias);
-        }
-    }
-}
-
-LayoutUnit RenderBlock::initialBlockOffsetForPainting() const
-{
-    ColumnInfo* colInfo = columnInfo();
-    LayoutUnit result = 0;
-    if (colInfo->progressionAxis() == ColumnInfo::BlockAxis && colInfo->progressionIsReversed()) {
-        LayoutRect colRect = columnRectAt(colInfo, 0);
-        result = isHorizontalWritingMode() ? colRect.y() : colRect.x();
-        result -= borderAndPaddingBefore();
-        if (style()->isFlippedBlocksWritingMode())
-            result = -result;
-    }
-    return result;
-}
-    
-LayoutUnit RenderBlock::blockDeltaForPaintingNextColumn() const
-{
-    ColumnInfo* colInfo = columnInfo();
-    LayoutUnit blockDelta = -colInfo->columnHeight();
-    LayoutUnit colGap = columnGap();
-    if (colInfo->progressionAxis() == ColumnInfo::BlockAxis) {
-        if (!colInfo->progressionIsReversed())
-            blockDelta = colGap;
-        else
-            blockDelta -= (colInfo->columnHeight() + colGap);
-    }
-    if (style()->isFlippedBlocksWritingMode())
-        blockDelta = -blockDelta;
-    return blockDelta;
-}
-
-void RenderBlock::paintColumnContents(PaintInfo& paintInfo, const LayoutPoint& paintOffset, bool paintingFloats)
-{
-    // We need to do multiple passes, breaking up our child painting into strips.
-    GraphicsContext* context = paintInfo.context;
-    ColumnInfo* colInfo = columnInfo();
-    unsigned colCount = columnCount(colInfo);
-    if (!colCount)
-        return;
-    LayoutUnit colGap = columnGap();
-    LayoutUnit currLogicalTopOffset = initialBlockOffsetForPainting();
-    LayoutUnit blockDelta = blockDeltaForPaintingNextColumn();
-    for (unsigned i = 0; i < colCount; i++) {
-        // For each rect, we clip to the rect, and then we adjust our coords.
-        LayoutRect colRect = columnRectAt(colInfo, i);
-        flipForWritingMode(colRect);
-        
-        LayoutUnit logicalLeftOffset = (isHorizontalWritingMode() ? colRect.x() : colRect.y()) - logicalLeftOffsetForContent();
-        LayoutSize offset = isHorizontalWritingMode() ? LayoutSize(logicalLeftOffset, currLogicalTopOffset) : LayoutSize(currLogicalTopOffset, logicalLeftOffset);
-        colRect.moveBy(paintOffset);
-        PaintInfo info(paintInfo);
-        info.rect.intersect(pixelSnappedIntRect(colRect));
-        
-        if (!info.rect.isEmpty()) {
-            GraphicsContextStateSaver stateSaver(*context);
-            LayoutRect clipRect(colRect);
-            
-            if (i < colCount - 1) {
-                if (isHorizontalWritingMode())
-                    clipRect.expand(colGap / 2, 0);
-                else
-                    clipRect.expand(0, colGap / 2);
-            }
-            // Each strip pushes a clip, since column boxes are specified as being
-            // like overflow:hidden.
-            // FIXME: Content and column rules that extend outside column boxes at the edges of the multi-column element
-            // are clipped according to the 'overflow' property.
-            context->clip(pixelSnappedIntRect(clipRect));
-
-            // Adjust our x and y when painting.
-            LayoutPoint adjustedPaintOffset = paintOffset + offset;
-            if (paintingFloats)
-                paintFloats(info, adjustedPaintOffset, paintInfo.phase == PaintPhaseSelection || paintInfo.phase == PaintPhaseTextClip);
-            else
-                paintContents(info, adjustedPaintOffset);
-        }
-        currLogicalTopOffset += blockDelta;
-    }
-}
-
-void RenderBlock::paintContents(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
-{
-    // Avoid painting descendants of the root element when stylesheets haven't loaded.  This eliminates FOUC.
-    // It's ok not to draw, because later on, when all the stylesheets do load, styleResolverChanged() on the Document
-    // will do a full repaint.
-    if (document()->didLayoutWithPendingStylesheets() && !isRenderView())
-        return;
-
-    if (childrenInline())
-        m_lineBoxes.paint(this, paintInfo, paintOffset);
-    else {
-        PaintPhase newPhase = (paintInfo.phase == PaintPhaseChildOutlines) ? PaintPhaseOutline : paintInfo.phase;
-        newPhase = (newPhase == PaintPhaseChildBlockBackgrounds) ? PaintPhaseChildBlockBackground : newPhase;
-
-        // We don't paint our own background, but we do let the kids paint their backgrounds.
-        PaintInfo paintInfoForChild(paintInfo);
-        paintInfoForChild.phase = newPhase;
-        paintInfoForChild.updateSubtreePaintRootForChildren(this);
-
-        // FIXME: Paint-time pagination is obsolete and is now only used by embedded WebViews inside AppKit
-        // NSViews. Do not add any more code for this.
-        bool usePrintRect = !view()->printRect().isEmpty();
-        paintChildren(paintInfo, paintOffset, paintInfoForChild, usePrintRect);
-    }
-}
-
-void RenderBlock::paintChildren(PaintInfo& paintInfo, const LayoutPoint& paintOffset, PaintInfo& paintInfoForChild, bool usePrintRect)
-{
-    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
-        if (!paintChild(child, paintInfo, paintOffset, paintInfoForChild, usePrintRect))
-            return;
-    }
-}
-
-bool RenderBlock::paintChild(RenderBox* child, PaintInfo& paintInfo, const LayoutPoint& paintOffset, PaintInfo& paintInfoForChild, bool usePrintRect)
-{
-    // Check for page-break-before: always, and if it's set, break and bail.
-    bool checkBeforeAlways = !childrenInline() && (usePrintRect && child->style()->pageBreakBefore() == PBALWAYS);
-    LayoutUnit absoluteChildY = paintOffset.y() + child->y();
-    if (checkBeforeAlways
-        && absoluteChildY > paintInfo.rect.y()
-        && absoluteChildY < paintInfo.rect.maxY()) {
-        view()->setBestTruncatedAt(absoluteChildY, this, true);
-        return false;
-    }
-
-    RenderView* renderView = view();
-    if (!child->isFloating() && child->isReplaced() && usePrintRect && child->height() <= renderView->printRect().height()) {
-        // Paginate block-level replaced elements.
-        if (absoluteChildY + child->height() > renderView->printRect().maxY()) {
-            if (absoluteChildY < renderView->truncatedAt())
-                renderView->setBestTruncatedAt(absoluteChildY, child);
-            // If we were able to truncate, don't paint.
-            if (absoluteChildY >= renderView->truncatedAt())
-                return false;
-        }
-    }
-
-    LayoutPoint childPoint = flipForWritingModeForChild(child, paintOffset);
-    if (!child->hasSelfPaintingLayer() && !child->isFloating())
-        child->paint(paintInfoForChild, childPoint);
-
-    // Check for page-break-after: always, and if it's set, break and bail.
-    bool checkAfterAlways = !childrenInline() && (usePrintRect && child->style()->pageBreakAfter() == PBALWAYS);
-    if (checkAfterAlways
-        && (absoluteChildY + child->height()) > paintInfo.rect.y()
-        && (absoluteChildY + child->height()) < paintInfo.rect.maxY()) {
-        view()->setBestTruncatedAt(absoluteChildY + child->height() + max<LayoutUnit>(0, child->collapsedMarginAfter()), this, true);
-        return false;
-    }
-    return true;
-}
-
-
-void RenderBlock::paintCaret(PaintInfo& paintInfo, const LayoutPoint& paintOffset, CaretType type)
-{
-    // Paint the caret if the FrameSelection says so or if caret browsing is enabled
-    bool caretBrowsing = frame()->settings() && frame()->settings()->caretBrowsingEnabled();
-    RenderObject* caretPainter;
-    bool isContentEditable;
-    if (type == CursorCaret) {
-        caretPainter = frame()->selection()->caretRenderer();
-        isContentEditable = frame()->selection()->rendererIsEditable();
-    } else {
-        caretPainter = frame()->page()->dragCaretController()->caretRenderer();
-        isContentEditable = frame()->page()->dragCaretController()->isContentEditable();
-    }
-
-    if (caretPainter == this && (isContentEditable || caretBrowsing)) {
-        if (type == CursorCaret)
-            frame()->selection()->paintCaret(paintInfo.context, paintOffset, paintInfo.rect);
-        else
-            frame()->page()->dragCaretController()->paintDragCaret(frame(), paintInfo.context, paintOffset, paintInfo.rect);
-    }
-}
-
-void RenderBlock::paintObject(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
-{
-    PaintPhase paintPhase = paintInfo.phase;
-
-    // 1. paint background, borders etc
-    if ((paintPhase == PaintPhaseBlockBackground || paintPhase == PaintPhaseChildBlockBackground) && style()->visibility() == VISIBLE) {
-        if (hasBoxDecorations())
-            paintBoxDecorations(paintInfo, paintOffset);
-        if (hasColumns() && !paintInfo.paintRootBackgroundOnly())
-            paintColumnRules(paintInfo, paintOffset);
-    }
-
-    if (paintPhase == PaintPhaseMask && style()->visibility() == VISIBLE) {
-        paintMask(paintInfo, paintOffset);
-        return;
-    }
-
-    // We're done.  We don't bother painting any children.
-    if (paintPhase == PaintPhaseBlockBackground || paintInfo.paintRootBackgroundOnly())
-        return;
-
-    // Adjust our painting position if we're inside a scrolled layer (e.g., an overflow:auto div).
-    LayoutPoint scrolledOffset = paintOffset;
-    if (hasOverflowClip())
-        scrolledOffset.move(-scrolledContentOffset());
-
-    // 2. paint contents
-    if (paintPhase != PaintPhaseSelfOutline) {
-        if (hasColumns())
-            paintColumnContents(paintInfo, scrolledOffset);
-        else
-            paintContents(paintInfo, scrolledOffset);
-    }
-
-    // 3. paint selection
-    // FIXME: Make this work with multi column layouts.  For now don't fill gaps.
-    bool isPrinting = document()->printing();
-    if (!isPrinting && !hasColumns())
-        paintSelection(paintInfo, scrolledOffset); // Fill in gaps in selection on lines and between blocks.
-
-    // 4. paint floats.
-    if (paintPhase == PaintPhaseFloat || paintPhase == PaintPhaseSelection || paintPhase == PaintPhaseTextClip) {
-        if (hasColumns())
-            paintColumnContents(paintInfo, scrolledOffset, true);
-        else
-            paintFloats(paintInfo, scrolledOffset, paintPhase == PaintPhaseSelection || paintPhase == PaintPhaseTextClip);
-    }
-
-    // 5. paint outline.
-    if ((paintPhase == PaintPhaseOutline || paintPhase == PaintPhaseSelfOutline) && hasOutline() && style()->visibility() == VISIBLE)
-        paintOutline(paintInfo, LayoutRect(paintOffset, size()));
-
-    // 6. paint continuation outlines.
-    if ((paintPhase == PaintPhaseOutline || paintPhase == PaintPhaseChildOutlines)) {
-        RenderInline* inlineCont = inlineElementContinuation();
-        if (inlineCont && inlineCont->hasOutline() && inlineCont->style()->visibility() == VISIBLE) {
-            RenderInline* inlineRenderer = toRenderInline(inlineCont->node()->renderer());
-            RenderBlock* cb = containingBlock();
-
-            bool inlineEnclosedInSelfPaintingLayer = false;
-            for (RenderBoxModelObject* box = inlineRenderer; box != cb; box = box->parent()->enclosingBoxModelObject()) {
-                if (box->hasSelfPaintingLayer()) {
-                    inlineEnclosedInSelfPaintingLayer = true;
-                    break;
-                }
-            }
-
-            // Do not add continuations for outline painting by our containing block if we are a relative positioned
-            // anonymous block (i.e. have our own layer), paint them straightaway instead. This is because a block depends on renderers in its continuation table being
-            // in the same layer. 
-            if (!inlineEnclosedInSelfPaintingLayer && !hasLayer())
-                cb->addContinuationWithOutline(inlineRenderer);
-            else if (!inlineRenderer->firstLineBox() || (!inlineEnclosedInSelfPaintingLayer && hasLayer()))
-                inlineRenderer->paintOutline(paintInfo, paintOffset - locationOffset() + inlineRenderer->containingBlock()->location());
-        }
-        paintContinuationOutlines(paintInfo, paintOffset);
-    }
-
-    // 7. paint caret.
-    // If the caret's node's render object's containing block is this block, and the paint action is PaintPhaseForeground,
-    // then paint the caret.
-    if (paintPhase == PaintPhaseForeground) {        
-        paintCaret(paintInfo, paintOffset, CursorCaret);
-        paintCaret(paintInfo, paintOffset, DragCaret);
-    }
-}
-
-LayoutPoint RenderBlock::flipFloatForWritingModeForChild(const FloatingObject* child, const LayoutPoint& point) const
-{
-    if (!style()->isFlippedBlocksWritingMode())
-        return point;
-    
-    // This is similar to RenderBox::flipForWritingModeForChild. We have to subtract out our left/top offsets twice, since
-    // it's going to get added back in. We hide this complication here so that the calling code looks normal for the unflipped
-    // case.
-    if (isHorizontalWritingMode())
-        return LayoutPoint(point.x(), point.y() + height() - child->renderer()->height() - 2 * yPositionForFloatIncludingMargin(child));
-    return LayoutPoint(point.x() + width() - child->renderer()->width() - 2 * xPositionForFloatIncludingMargin(child), point.y());
-}
-
-void RenderBlock::paintFloats(PaintInfo& paintInfo, const LayoutPoint& paintOffset, bool preservePhase)
-{
-    if (!m_floatingObjects)
-        return;
-
-    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    FloatingObjectSetIterator end = floatingObjectSet.end();
-    for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-        FloatingObject* r = *it;
-        // Only paint the object if our m_shouldPaint flag is set.
-        if (r->shouldPaint() && !r->m_renderer->hasSelfPaintingLayer()) {
-            PaintInfo currentPaintInfo(paintInfo);
-            currentPaintInfo.phase = preservePhase ? paintInfo.phase : PaintPhaseBlockBackground;
-            LayoutPoint childPoint = flipFloatForWritingModeForChild(r, LayoutPoint(paintOffset.x() + xPositionForFloatIncludingMargin(r) - r->m_renderer->x(), paintOffset.y() + yPositionForFloatIncludingMargin(r) - r->m_renderer->y()));
-            r->m_renderer->paint(currentPaintInfo, childPoint);
-            if (!preservePhase) {
-                currentPaintInfo.phase = PaintPhaseChildBlockBackgrounds;
-                r->m_renderer->paint(currentPaintInfo, childPoint);
-                currentPaintInfo.phase = PaintPhaseFloat;
-                r->m_renderer->paint(currentPaintInfo, childPoint);
-                currentPaintInfo.phase = PaintPhaseForeground;
-                r->m_renderer->paint(currentPaintInfo, childPoint);
-                currentPaintInfo.phase = PaintPhaseOutline;
-                r->m_renderer->paint(currentPaintInfo, childPoint);
-            }
-        }
-    }
-}
-
-RenderInline* RenderBlock::inlineElementContinuation() const
-{ 
-    RenderBoxModelObject* continuation = this->continuation();
-    return continuation && continuation->isInline() ? toRenderInline(continuation) : 0;
-}
-
-RenderBlock* RenderBlock::blockElementContinuation() const
-{
-    RenderBoxModelObject* currentContinuation = continuation();
-    if (!currentContinuation || currentContinuation->isInline())
-        return 0;
-    RenderBlock* nextContinuation = toRenderBlock(currentContinuation);
-    if (nextContinuation->isAnonymousBlock())
-        return nextContinuation->blockElementContinuation();
-    return nextContinuation;
-}
-    
-static ContinuationOutlineTableMap* continuationOutlineTable()
-{
-    DEFINE_STATIC_LOCAL(ContinuationOutlineTableMap, table, ());
-    return &table;
-}
-
-void RenderBlock::addContinuationWithOutline(RenderInline* flow)
-{
-    // We can't make this work if the inline is in a layer.  We'll just rely on the broken
-    // way of painting.
-    ASSERT(!flow->layer() && !flow->isInlineElementContinuation());
-    
-    ContinuationOutlineTableMap* table = continuationOutlineTable();
-    ListHashSet<RenderInline*>* continuations = table->get(this);
-    if (!continuations) {
-        continuations = new ListHashSet<RenderInline*>;
-        table->set(this, adoptPtr(continuations));
-    }
-    
-    continuations->add(flow);
-}
-
-bool RenderBlock::paintsContinuationOutline(RenderInline* flow)
-{
-    ContinuationOutlineTableMap* table = continuationOutlineTable();
-    if (table->isEmpty())
-        return false;
-        
-    ListHashSet<RenderInline*>* continuations = table->get(this);
-    if (!continuations)
-        return false;
-
-    return continuations->contains(flow);
-}
-
-void RenderBlock::paintContinuationOutlines(PaintInfo& info, const LayoutPoint& paintOffset)
-{
-    ContinuationOutlineTableMap* table = continuationOutlineTable();
-    if (table->isEmpty())
-        return;
-        
-    OwnPtr<ListHashSet<RenderInline*> > continuations = table->take(this);
-    if (!continuations)
-        return;
-
-    LayoutPoint accumulatedPaintOffset = paintOffset;
-    // Paint each continuation outline.
-    ListHashSet<RenderInline*>::iterator end = continuations->end();
-    for (ListHashSet<RenderInline*>::iterator it = continuations->begin(); it != end; ++it) {
-        // Need to add in the coordinates of the intervening blocks.
-        RenderInline* flow = *it;
-        RenderBlock* block = flow->containingBlock();
-        for ( ; block && block != this; block = block->containingBlock())
-            accumulatedPaintOffset.moveBy(block->location());
-        ASSERT(block);   
-        flow->paintOutline(info, accumulatedPaintOffset);
-    }
-}
-
-bool RenderBlock::shouldPaintSelectionGaps() const
-{
-    return selectionState() != SelectionNone && style()->visibility() == VISIBLE && isSelectionRoot();
-}
-
-bool RenderBlock::isSelectionRoot() const
-{
-    if (isPseudoElement())
-        return false;
-    ASSERT(node() || isAnonymous());
-        
-    // FIXME: Eventually tables should have to learn how to fill gaps between cells, at least in simple non-spanning cases.
-    if (isTable())
-        return false;
-        
-    if (isBody() || isRoot() || hasOverflowClip()
-        || isPositioned() || isFloating()
-        || isTableCell() || isInlineBlockOrInlineTable()
-        || hasTransform() || hasReflection() || hasMask() || isWritingModeRoot()
-        || isRenderFlowThread())
-        return true;
-    
-    if (view() && view()->selectionStart()) {
-        Node* startElement = view()->selectionStart()->node();
-        if (startElement && startElement->rootEditableElement() == node())
-            return true;
-    }
-    
-    return false;
-}
-
-GapRects RenderBlock::selectionGapRectsForRepaint(const RenderLayerModelObject* repaintContainer)
-{
-    ASSERT(!needsLayout());
-
-    if (!shouldPaintSelectionGaps())
-        return GapRects();
-
-    TransformState transformState(TransformState::ApplyTransformDirection, FloatPoint());
-    mapLocalToContainer(repaintContainer, transformState, ApplyContainerFlip | UseTransforms);
-    LayoutPoint offsetFromRepaintContainer = roundedLayoutPoint(transformState.mappedPoint());
-
-    if (hasOverflowClip())
-        offsetFromRepaintContainer -= scrolledContentOffset();
-
-    LogicalSelectionOffsetCaches cache(this);
-    LayoutUnit lastTop = 0;
-    LayoutUnit lastLeft = logicalLeftSelectionOffset(this, lastTop, cache);
-    LayoutUnit lastRight = logicalRightSelectionOffset(this, lastTop, cache);
-    
-    return selectionGaps(this, offsetFromRepaintContainer, IntSize(), lastTop, lastLeft, lastRight, cache);
-}
-
-void RenderBlock::paintSelection(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
-{
-    if (shouldPaintSelectionGaps() && paintInfo.phase == PaintPhaseForeground) {
-        LogicalSelectionOffsetCaches cache(this);
-        LayoutUnit lastTop = 0;
-        LayoutUnit lastLeft = logicalLeftSelectionOffset(this, lastTop, cache);
-        LayoutUnit lastRight = logicalRightSelectionOffset(this, lastTop, cache);
-        GraphicsContextStateSaver stateSaver(*paintInfo.context);
-
-        LayoutRect gapRectsBounds = selectionGaps(this, paintOffset, LayoutSize(), lastTop, lastLeft, lastRight, cache, &paintInfo);
-        if (!gapRectsBounds.isEmpty()) {
-            if (RenderLayer* layer = enclosingLayer()) {
-                gapRectsBounds.moveBy(-paintOffset);
-                if (!hasLayer()) {
-                    LayoutRect localBounds(gapRectsBounds);
-                    flipForWritingMode(localBounds);
-                    gapRectsBounds = localToContainerQuad(FloatRect(localBounds), layer->renderer()).enclosingBoundingBox();
-                    if (layer->renderer()->hasOverflowClip())
-                        gapRectsBounds.move(layer->renderBox()->scrolledContentOffset());
-                }
-                layer->addBlockSelectionGapsBounds(gapRectsBounds);
-            }
-        }
-    }
-}
-
-static void clipOutPositionedObjects(const PaintInfo* paintInfo, const LayoutPoint& offset, TrackedRendererListHashSet* positionedObjects)
-{
-    if (!positionedObjects)
-        return;
-    
-    TrackedRendererListHashSet::const_iterator end = positionedObjects->end();
-    for (TrackedRendererListHashSet::const_iterator it = positionedObjects->begin(); it != end; ++it) {
-        RenderBox* r = *it;
-        paintInfo->context->clipOut(IntRect(offset.x() + r->x(), offset.y() + r->y(), r->width(), r->height()));
-    }
-}
-
-static LayoutUnit blockDirectionOffset(RenderBlock* rootBlock, const LayoutSize& offsetFromRootBlock)
-{
-    return rootBlock->isHorizontalWritingMode() ? offsetFromRootBlock.height() : offsetFromRootBlock.width();
-}
-
-static LayoutUnit inlineDirectionOffset(RenderBlock* rootBlock, const LayoutSize& offsetFromRootBlock)
-{
-    return rootBlock->isHorizontalWritingMode() ? offsetFromRootBlock.width() : offsetFromRootBlock.height();
-}
-
-LayoutRect RenderBlock::logicalRectToPhysicalRect(const LayoutPoint& rootBlockPhysicalPosition, const LayoutRect& logicalRect)
-{
-    LayoutRect result;
-    if (isHorizontalWritingMode())
-        result = logicalRect;
-    else
-        result = LayoutRect(logicalRect.y(), logicalRect.x(), logicalRect.height(), logicalRect.width());
-    flipForWritingMode(result);
-    result.moveBy(rootBlockPhysicalPosition);
-    return result;
-}
-
-GapRects RenderBlock::selectionGaps(RenderBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
-    LayoutUnit& lastLogicalTop, LayoutUnit& lastLogicalLeft, LayoutUnit& lastLogicalRight, const LogicalSelectionOffsetCaches& cache, const PaintInfo* paintInfo)
-{
-    // IMPORTANT: Callers of this method that intend for painting to happen need to do a save/restore.
-    // Clip out floating and positioned objects when painting selection gaps.
-    if (paintInfo) {
-        // Note that we don't clip out overflow for positioned objects.  We just stick to the border box.
-        LayoutRect flippedBlockRect(offsetFromRootBlock.width(), offsetFromRootBlock.height(), width(), height());
-        rootBlock->flipForWritingMode(flippedBlockRect);
-        flippedBlockRect.moveBy(rootBlockPhysicalPosition);
-        clipOutPositionedObjects(paintInfo, flippedBlockRect.location(), positionedObjects());
-        if (isBody() || isRoot()) // The <body> must make sure to examine its containingBlock's positioned objects.
-            for (RenderBlock* cb = containingBlock(); cb && !cb->isRenderView(); cb = cb->containingBlock())
-                clipOutPositionedObjects(paintInfo, LayoutPoint(cb->x(), cb->y()), cb->positionedObjects()); // FIXME: Not right for flipped writing modes.
-        if (m_floatingObjects) {
-            const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-            FloatingObjectSetIterator end = floatingObjectSet.end();
-            for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-                FloatingObject* r = *it;
-                LayoutRect floatBox(offsetFromRootBlock.width() + xPositionForFloatIncludingMargin(r),
-                                    offsetFromRootBlock.height() + yPositionForFloatIncludingMargin(r),
-                                    r->m_renderer->width(), r->m_renderer->height());
-                rootBlock->flipForWritingMode(floatBox);
-                floatBox.move(rootBlockPhysicalPosition.x(), rootBlockPhysicalPosition.y());
-                paintInfo->context->clipOut(pixelSnappedIntRect(floatBox));
-            }
-        }
-    }
-
-    // FIXME: overflow: auto/scroll regions need more math here, since painting in the border box is different from painting in the padding box (one is scrolled, the other is
-    // fixed).
-    GapRects result;
-    if (!isBlockFlow()) // FIXME: Make multi-column selection gap filling work someday.
-        return result;
-
-    if (hasColumns() || hasTransform() || style()->columnSpan()) {
-        // FIXME: We should learn how to gap fill multiple columns and transforms eventually.
-        lastLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalHeight();
-        lastLogicalLeft = logicalLeftSelectionOffset(rootBlock, logicalHeight(), cache);
-        lastLogicalRight = logicalRightSelectionOffset(rootBlock, logicalHeight(), cache);
-        return result;
-    }
-
-    if (childrenInline())
-        result = inlineSelectionGaps(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, lastLogicalTop, lastLogicalLeft, lastLogicalRight, cache, paintInfo);
-    else
-        result = blockSelectionGaps(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, lastLogicalTop, lastLogicalLeft, lastLogicalRight, cache, paintInfo);
-
-    // Go ahead and fill the vertical gap all the way to the bottom of our block if the selection extends past our block.
-    if (rootBlock == this && (selectionState() != SelectionBoth && selectionState() != SelectionEnd)) {
-        result.uniteCenter(blockSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock,
-            lastLogicalTop, lastLogicalLeft, lastLogicalRight, logicalHeight(), cache, paintInfo));
-    }
-
-    return result;
-}
-
-GapRects RenderBlock::inlineSelectionGaps(RenderBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
-    LayoutUnit& lastLogicalTop, LayoutUnit& lastLogicalLeft, LayoutUnit& lastLogicalRight, const LogicalSelectionOffsetCaches& cache, const PaintInfo* paintInfo)
-{
-    GapRects result;
-
-    bool containsStart = selectionState() == SelectionStart || selectionState() == SelectionBoth;
-
-    if (!firstLineBox()) {
-        if (containsStart) {
-            // Go ahead and update our lastLogicalTop to be the bottom of the block.  <hr>s or empty blocks with height can trip this
-            // case.
-            lastLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalHeight();
-            lastLogicalLeft = logicalLeftSelectionOffset(rootBlock, logicalHeight(), cache);
-            lastLogicalRight = logicalRightSelectionOffset(rootBlock, logicalHeight(), cache);
-        }
-        return result;
-    }
-
-    RootInlineBox* lastSelectedLine = 0;
-    RootInlineBox* curr;
-    for (curr = firstRootBox(); curr && !curr->hasSelectedChildren(); curr = curr->nextRootBox()) { }
-
-    // Now paint the gaps for the lines.
-    for (; curr && curr->hasSelectedChildren(); curr = curr->nextRootBox()) {
-        LayoutUnit selTop =  curr->selectionTopAdjustedForPrecedingBlock();
-        LayoutUnit selHeight = curr->selectionHeightAdjustedForPrecedingBlock();
-
-        if (!containsStart && !lastSelectedLine &&
-            selectionState() != SelectionStart && selectionState() != SelectionBoth)
-            result.uniteCenter(blockSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, lastLogicalTop, lastLogicalLeft, lastLogicalRight, selTop, cache, paintInfo));
-        
-        LayoutRect logicalRect(curr->logicalLeft(), selTop, curr->logicalWidth(), selTop + selHeight);
-        logicalRect.move(isHorizontalWritingMode() ? offsetFromRootBlock : offsetFromRootBlock.transposedSize());
-        LayoutRect physicalRect = rootBlock->logicalRectToPhysicalRect(rootBlockPhysicalPosition, logicalRect);
-        if (!paintInfo || (isHorizontalWritingMode() && physicalRect.y() < paintInfo->rect.maxY() && physicalRect.maxY() > paintInfo->rect.y())
-            || (!isHorizontalWritingMode() && physicalRect.x() < paintInfo->rect.maxX() && physicalRect.maxX() > paintInfo->rect.x()))
-            result.unite(curr->lineSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, selTop, selHeight, cache, paintInfo));
-
-        lastSelectedLine = curr;
-    }
-
-    if (containsStart && !lastSelectedLine)
-        // VisibleSelection must start just after our last line.
-        lastSelectedLine = lastRootBox();
-
-    if (lastSelectedLine && selectionState() != SelectionEnd && selectionState() != SelectionBoth) {
-        // Go ahead and update our lastY to be the bottom of the last selected line.
-        lastLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + lastSelectedLine->selectionBottom();
-        lastLogicalLeft = logicalLeftSelectionOffset(rootBlock, lastSelectedLine->selectionBottom(), cache);
-        lastLogicalRight = logicalRightSelectionOffset(rootBlock, lastSelectedLine->selectionBottom(), cache);
-    }
-    return result;
-}
-
-GapRects RenderBlock::blockSelectionGaps(RenderBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
-    LayoutUnit& lastLogicalTop, LayoutUnit& lastLogicalLeft, LayoutUnit& lastLogicalRight, const LogicalSelectionOffsetCaches& cache, const PaintInfo* paintInfo)
-{
-    GapRects result;
-
-    // Go ahead and jump right to the first block child that contains some selected objects.
-    RenderBox* curr;
-    for (curr = firstChildBox(); curr && curr->selectionState() == SelectionNone; curr = curr->nextSiblingBox()) { }
-    
-    if (!curr)
-        return result;
-
-    LogicalSelectionOffsetCaches childCache(this, cache);
-
-    for (bool sawSelectionEnd = false; curr && !sawSelectionEnd; curr = curr->nextSiblingBox()) {
-        SelectionState childState = curr->selectionState();
-        if (childState == SelectionBoth || childState == SelectionEnd)
-            sawSelectionEnd = true;
-
-        if (curr->isFloatingOrOutOfFlowPositioned())
-            continue; // We must be a normal flow object in order to even be considered.
-
-        if (curr->isInFlowPositioned() && curr->hasLayer()) {
-            // If the relposition offset is anything other than 0, then treat this just like an absolute positioned element.
-            // Just disregard it completely.
-            LayoutSize relOffset = curr->layer()->offsetForInFlowPosition();
-            if (relOffset.width() || relOffset.height())
-                continue;
-        }
-
-        bool paintsOwnSelection = curr->shouldPaintSelectionGaps() || curr->isTable(); // FIXME: Eventually we won't special-case table like this.
-        bool fillBlockGaps = paintsOwnSelection || (curr->canBeSelectionLeaf() && childState != SelectionNone);
-        if (fillBlockGaps) {
-            // We need to fill the vertical gap above this object.
-            if (childState == SelectionEnd || childState == SelectionInside) {
-                // Fill the gap above the object.
-                result.uniteCenter(blockSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock,
-                    lastLogicalTop, lastLogicalLeft, lastLogicalRight, curr->logicalTop(), cache, paintInfo));
-            }
-
-            // Only fill side gaps for objects that paint their own selection if we know for sure the selection is going to extend all the way *past*
-            // our object.  We know this if the selection did not end inside our object.
-            if (paintsOwnSelection && (childState == SelectionStart || sawSelectionEnd))
-                childState = SelectionNone;
-
-            // Fill side gaps on this object based off its state.
-            bool leftGap, rightGap;
-            getSelectionGapInfo(childState, leftGap, rightGap);
-
-            if (leftGap)
-                result.uniteLeft(logicalLeftSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, this, curr->logicalLeft(), curr->logicalTop(), curr->logicalHeight(), cache, paintInfo));
-            if (rightGap)
-                result.uniteRight(logicalRightSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, this, curr->logicalRight(), curr->logicalTop(), curr->logicalHeight(), cache, paintInfo));
-
-            // Update lastLogicalTop to be just underneath the object.  lastLogicalLeft and lastLogicalRight extend as far as
-            // they can without bumping into floating or positioned objects.  Ideally they will go right up
-            // to the border of the root selection block.
-            lastLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + curr->logicalBottom();
-            lastLogicalLeft = logicalLeftSelectionOffset(rootBlock, curr->logicalBottom(), cache);
-            lastLogicalRight = logicalRightSelectionOffset(rootBlock, curr->logicalBottom(), cache);
-        } else if (childState != SelectionNone) {
-            // We must be a block that has some selected object inside it.  Go ahead and recur.
-            result.unite(toRenderBlock(curr)->selectionGaps(rootBlock, rootBlockPhysicalPosition, LayoutSize(offsetFromRootBlock.width() + curr->x(), offsetFromRootBlock.height() + curr->y()), 
-                lastLogicalTop, lastLogicalLeft, lastLogicalRight, childCache, paintInfo));
-        }
-    }
-    return result;
-}
-
-LayoutRect RenderBlock::blockSelectionGap(RenderBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
-    LayoutUnit lastLogicalTop, LayoutUnit lastLogicalLeft, LayoutUnit lastLogicalRight, LayoutUnit logicalBottom, const LogicalSelectionOffsetCaches& cache, const PaintInfo* paintInfo)
-{
-    LayoutUnit logicalTop = lastLogicalTop;
-    LayoutUnit logicalHeight = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalBottom - logicalTop;
-    if (logicalHeight <= 0)
-        return LayoutRect();
-
-    // Get the selection offsets for the bottom of the gap
-    LayoutUnit logicalLeft = max(lastLogicalLeft, logicalLeftSelectionOffset(rootBlock, logicalBottom, cache));
-    LayoutUnit logicalRight = min(lastLogicalRight, logicalRightSelectionOffset(rootBlock, logicalBottom, cache));
-    LayoutUnit logicalWidth = logicalRight - logicalLeft;
-    if (logicalWidth <= 0)
-        return LayoutRect();
-
-    LayoutRect gapRect = rootBlock->logicalRectToPhysicalRect(rootBlockPhysicalPosition, LayoutRect(logicalLeft, logicalTop, logicalWidth, logicalHeight));
-    if (paintInfo)
-        paintInfo->context->fillRect(pixelSnappedIntRect(gapRect), selectionBackgroundColor(), style()->colorSpace());
-    return gapRect;
-}
-
-LayoutRect RenderBlock::logicalLeftSelectionGap(RenderBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
-    RenderObject* selObj, LayoutUnit logicalLeft, LayoutUnit logicalTop, LayoutUnit logicalHeight, const LogicalSelectionOffsetCaches& cache, const PaintInfo* paintInfo)
-{
-    LayoutUnit rootBlockLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalTop;
-    LayoutUnit rootBlockLogicalLeft = max(logicalLeftSelectionOffset(rootBlock, logicalTop, cache), logicalLeftSelectionOffset(rootBlock, logicalTop + logicalHeight, cache));
-    LayoutUnit rootBlockLogicalRight = min(inlineDirectionOffset(rootBlock, offsetFromRootBlock) + floorToInt(logicalLeft),
-        min(logicalRightSelectionOffset(rootBlock, logicalTop, cache), logicalRightSelectionOffset(rootBlock, logicalTop + logicalHeight, cache)));
-    LayoutUnit rootBlockLogicalWidth = rootBlockLogicalRight - rootBlockLogicalLeft;
-    if (rootBlockLogicalWidth <= 0)
-        return LayoutRect();
-
-    LayoutRect gapRect = rootBlock->logicalRectToPhysicalRect(rootBlockPhysicalPosition, LayoutRect(rootBlockLogicalLeft, rootBlockLogicalTop, rootBlockLogicalWidth, logicalHeight));
-    if (paintInfo)
-        paintInfo->context->fillRect(pixelSnappedIntRect(gapRect), selObj->selectionBackgroundColor(), selObj->style()->colorSpace());
-    return gapRect;
-}
-
-LayoutRect RenderBlock::logicalRightSelectionGap(RenderBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
-    RenderObject* selObj, LayoutUnit logicalRight, LayoutUnit logicalTop, LayoutUnit logicalHeight, const LogicalSelectionOffsetCaches& cache, const PaintInfo* paintInfo)
-{
-    LayoutUnit rootBlockLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalTop;
-    LayoutUnit rootBlockLogicalLeft = max(inlineDirectionOffset(rootBlock, offsetFromRootBlock) + floorToInt(logicalRight),
-        max(logicalLeftSelectionOffset(rootBlock, logicalTop, cache), logicalLeftSelectionOffset(rootBlock, logicalTop + logicalHeight, cache)));
-    LayoutUnit rootBlockLogicalRight = min(logicalRightSelectionOffset(rootBlock, logicalTop, cache), logicalRightSelectionOffset(rootBlock, logicalTop + logicalHeight, cache));
-    LayoutUnit rootBlockLogicalWidth = rootBlockLogicalRight - rootBlockLogicalLeft;
-    if (rootBlockLogicalWidth <= 0)
-        return LayoutRect();
-
-    LayoutRect gapRect = rootBlock->logicalRectToPhysicalRect(rootBlockPhysicalPosition, LayoutRect(rootBlockLogicalLeft, rootBlockLogicalTop, rootBlockLogicalWidth, logicalHeight));
-    if (paintInfo)
-        paintInfo->context->fillRect(pixelSnappedIntRect(gapRect), selObj->selectionBackgroundColor(), selObj->style()->colorSpace());
-    return gapRect;
-}
-
-void RenderBlock::getSelectionGapInfo(SelectionState state, bool& leftGap, bool& rightGap)
-{
-    bool ltr = style()->isLeftToRightDirection();
-    leftGap = (state == RenderObject::SelectionInside) ||
-              (state == RenderObject::SelectionEnd && ltr) ||
-              (state == RenderObject::SelectionStart && !ltr);
-    rightGap = (state == RenderObject::SelectionInside) ||
-               (state == RenderObject::SelectionStart && ltr) ||
-               (state == RenderObject::SelectionEnd && !ltr);
-}
-
-LayoutUnit RenderBlock::logicalLeftSelectionOffset(RenderBlock* rootBlock, LayoutUnit position, const LogicalSelectionOffsetCaches& cache)
-{
-    LayoutUnit logicalLeft = logicalLeftOffsetForLine(position, false);
-    if (logicalLeft == logicalLeftOffsetForContent()) {
-        if (rootBlock != this) // The border can potentially be further extended by our containingBlock().
-            return cache.containingBlockInfo(this).logicalLeftSelectionOffset(rootBlock, position + logicalTop());
-        return logicalLeft;
-    } else {
-        RenderBlock* cb = this;
-        const LogicalSelectionOffsetCaches* currentCache = &cache;
-        while (cb != rootBlock) {
-            logicalLeft += cb->logicalLeft();
-
-            ASSERT(currentCache);
-            const LogicalSelectionOffsetCaches::ContainingBlockInfo& info = currentCache->containingBlockInfo(cb);
-            cb = info.block();
-            currentCache = info.cache();
-        }
-    }
-    return logicalLeft;
-}
-
-LayoutUnit RenderBlock::logicalRightSelectionOffset(RenderBlock* rootBlock, LayoutUnit position, const LogicalSelectionOffsetCaches& cache)
-{
-    LayoutUnit logicalRight = logicalRightOffsetForLine(position, false);
-    if (logicalRight == logicalRightOffsetForContent()) {
-        if (rootBlock != this) // The border can potentially be further extended by our containingBlock().
-            return cache.containingBlockInfo(this).logicalRightSelectionOffset(rootBlock, position + logicalTop());
-        return logicalRight;
-    } else {
-        RenderBlock* cb = this;
-        const LogicalSelectionOffsetCaches* currentCache = &cache;
-        while (cb != rootBlock) {
-            logicalRight += cb->logicalLeft();
-
-            ASSERT(currentCache);
-            const LogicalSelectionOffsetCaches::ContainingBlockInfo& info = currentCache->containingBlockInfo(cb);
-            cb = info.block();
-            currentCache = info.cache();
-        }
-    }
-    return logicalRight;
-}
-
-RenderBlock* RenderBlock::blockBeforeWithinSelectionRoot(LayoutSize& offset) const
-{
-    if (isSelectionRoot())
-        return 0;
-
-    const RenderObject* object = this;
-    RenderObject* sibling;
-    do {
-        sibling = object->previousSibling();
-        while (sibling && (!sibling->isRenderBlock() || toRenderBlock(sibling)->isSelectionRoot()))
-            sibling = sibling->previousSibling();
-
-        offset -= LayoutSize(toRenderBlock(object)->logicalLeft(), toRenderBlock(object)->logicalTop());
-        object = object->parent();
-    } while (!sibling && object && object->isRenderBlock() && !toRenderBlock(object)->isSelectionRoot());
-
-    if (!sibling)
-        return 0;
-
-    RenderBlock* beforeBlock = toRenderBlock(sibling);
-
-    offset += LayoutSize(beforeBlock->logicalLeft(), beforeBlock->logicalTop());
-
-    RenderObject* child = beforeBlock->lastChild();
-    while (child && child->isRenderBlock()) {
-        beforeBlock = toRenderBlock(child);
-        offset += LayoutSize(beforeBlock->logicalLeft(), beforeBlock->logicalTop());
-        child = beforeBlock->lastChild();
-    }
-    return beforeBlock;
-}
-
-void RenderBlock::insertIntoTrackedRendererMaps(RenderBox* descendant, TrackedDescendantsMap*& descendantsMap, TrackedContainerMap*& containerMap)
-{
-    if (!descendantsMap) {
-        descendantsMap = new TrackedDescendantsMap;
-        containerMap = new TrackedContainerMap;
-    }
-    
-    TrackedRendererListHashSet* descendantSet = descendantsMap->get(this);
-    if (!descendantSet) {
-        descendantSet = new TrackedRendererListHashSet;
-        descendantsMap->set(this, adoptPtr(descendantSet));
-    }
-    bool added = descendantSet->add(descendant).isNewEntry;
-    if (!added) {
-        ASSERT(containerMap->get(descendant));
-        ASSERT(containerMap->get(descendant)->contains(this));
-        return;
-    }
-    
-    HashSet<RenderBlock*>* containerSet = containerMap->get(descendant);
-    if (!containerSet) {
-        containerSet = new HashSet<RenderBlock*>;
-        containerMap->set(descendant, adoptPtr(containerSet));
-    }
-    ASSERT(!containerSet->contains(this));
-    containerSet->add(this);
-}
-
-void RenderBlock::removeFromTrackedRendererMaps(RenderBox* descendant, TrackedDescendantsMap*& descendantsMap, TrackedContainerMap*& containerMap)
-{
-    if (!descendantsMap)
-        return;
-    
-    OwnPtr<HashSet<RenderBlock*> > containerSet = containerMap->take(descendant);
-    if (!containerSet)
-        return;
-    
-    HashSet<RenderBlock*>::iterator end = containerSet->end();
-    for (HashSet<RenderBlock*>::iterator it = containerSet->begin(); it != end; ++it) {
-        RenderBlock* container = *it;
-
-        // FIXME: Disabling this assert temporarily until we fix the layout
-        // bugs associated with positioned objects not properly cleared from
-        // their ancestor chain before being moved. See webkit bug 93766.
-        // ASSERT(descendant->isDescendantOf(container));
-
-        TrackedDescendantsMap::iterator descendantsMapIterator = descendantsMap->find(container);
-        ASSERT(descendantsMapIterator != descendantsMap->end());
-        if (descendantsMapIterator == descendantsMap->end())
-            continue;
-        TrackedRendererListHashSet* descendantSet = descendantsMapIterator->value.get();
-        ASSERT(descendantSet->contains(descendant));
-        descendantSet->remove(descendant);
-        if (descendantSet->isEmpty())
-            descendantsMap->remove(descendantsMapIterator);
-    }
-}
-
-TrackedRendererListHashSet* RenderBlock::positionedObjects() const
-{
-    if (gPositionedDescendantsMap)
-        return gPositionedDescendantsMap->get(this);
-    return 0;
-}
-
-void RenderBlock::insertPositionedObject(RenderBox* o)
-{
-    ASSERT(!isAnonymousBlock());
-
-    if (o->isRenderFlowThread())
-        return;
-    
-    insertIntoTrackedRendererMaps(o, gPositionedDescendantsMap, gPositionedContainerMap);
-}
-
-void RenderBlock::removePositionedObject(RenderBox* o)
-{
-    removeFromTrackedRendererMaps(o, gPositionedDescendantsMap, gPositionedContainerMap);
-}
-
-void RenderBlock::removePositionedObjects(RenderBlock* o, ContainingBlockState containingBlockState)
-{
-    TrackedRendererListHashSet* positionedDescendants = positionedObjects();
-    if (!positionedDescendants)
-        return;
-    
-    RenderBox* r;
-    
-    TrackedRendererListHashSet::iterator end = positionedDescendants->end();
-    
-    Vector<RenderBox*, 16> deadObjects;
-
-    for (TrackedRendererListHashSet::iterator it = positionedDescendants->begin(); it != end; ++it) {
-        r = *it;
-        if (!o || r->isDescendantOf(o)) {
-            if (containingBlockState == NewContainingBlock)
-                r->setChildNeedsLayout(true, MarkOnlyThis);
-            
-            // It is parent blocks job to add positioned child to positioned objects list of its containing block
-            // Parent layout needs to be invalidated to ensure this happens.
-            RenderObject* p = r->parent();
-            while (p && !p->isRenderBlock())
-                p = p->parent();
-            if (p)
-                p->setChildNeedsLayout(true);
-            
-            deadObjects.append(r);
-        }
-    }
-    
-    for (unsigned i = 0; i < deadObjects.size(); i++)
-        removePositionedObject(deadObjects.at(i));
-}
-
-void RenderBlock::removeFloatingObjects()
+RenderBlock* RenderBlock::blockElementContinuation() const
 {
-    if (!m_floatingObjects)
-        return;
-
-    deleteAllValues(m_floatingObjects->set());
-    m_floatingObjects->clear();
+    RenderBoxModelObject* currentContinuation = continuation();
+    if (!currentContinuation || currentContinuation->isInline())
+        return nullptr;
+    RenderBlock& nextContinuation = downcast<RenderBlock>(*currentContinuation);
+    if (nextContinuation.isAnonymousBlock())
+        return nextContinuation.blockElementContinuation();
+    return &nextContinuation;
 }
-
-RenderBlock::FloatingObject* RenderBlock::insertFloatingObject(RenderBox* o)
-{
-    ASSERT(o->isFloating());
-
-    // Create the list of special objects if we don't aleady have one
-    if (!m_floatingObjects)
-        createFloatingObjects();
-    else {
-        // Don't insert the object again if it's already in the list
-        const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-        FloatingObjectSetIterator it = floatingObjectSet.find<RenderBox*, FloatingObjectHashTranslator>(o);
-        if (it != floatingObjectSet.end())
-            return *it;
-    }
-
-    // Create the special object entry & append it to the list
-
-    FloatingObject* newObj = new FloatingObject(o->style()->floating());
-    
-    // Our location is irrelevant if we're unsplittable or no pagination is in effect.
-    // Just go ahead and lay out the float.
-    bool isChildRenderBlock = o->isRenderBlock();
-    if (isChildRenderBlock && !o->needsLayout() && view()->layoutState()->pageLogicalHeightChanged())
-        o->setChildNeedsLayout(true, MarkOnlyThis);
-            
-    bool needsBlockDirectionLocationSetBeforeLayout = isChildRenderBlock && view()->layoutState()->needsBlockDirectionLocationSetBeforeLayout();
-    if (!needsBlockDirectionLocationSetBeforeLayout || isWritingModeRoot()) // We are unsplittable if we're a block flow root.
-        o->layoutIfNeeded();
-    else {
-        o->updateLogicalWidth();
-        o->computeAndSetBlockDirectionMargins(this);
-    }
-
-    setLogicalWidthForFloat(newObj, logicalWidthForChild(o) + marginStartForChild(o) + marginEndForChild(o));
-
-#if ENABLE(CSS_SHAPES)
-    if (ShapeOutsideInfo* shapeOutside = o->shapeOutsideInfo())
-        shapeOutside->setShapeSize(logicalWidthForChild(o), logicalHeightForChild(o));
-#endif
-
-    newObj->setShouldPaint(!o->hasSelfPaintingLayer()); // If a layer exists, the float will paint itself. Otherwise someone else will.
-    newObj->setIsDescendant(true);
-    newObj->m_renderer = o;
-
-    m_floatingObjects->add(newObj);
     
-    return newObj;
-}
-
-void RenderBlock::removeFloatingObject(RenderBox* o)
-{
-    if (m_floatingObjects) {
-        const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-        FloatingObjectSetIterator it = floatingObjectSet.find<RenderBox*, FloatingObjectHashTranslator>(o);
-        if (it != floatingObjectSet.end()) {
-            FloatingObject* r = *it;
-            if (childrenInline()) {
-                LayoutUnit logicalTop = logicalTopForFloat(r);
-                LayoutUnit logicalBottom = logicalBottomForFloat(r);
-
-                // Fix for https://bugs.webkit.org/show_bug.cgi?id=54995.
-                if (logicalBottom < 0 || logicalBottom < logicalTop || logicalTop == LayoutUnit::max())
-                    logicalBottom = LayoutUnit::max();
-                else {
-                    // Special-case zero- and less-than-zero-height floats: those don't touch
-                    // the line that they're on, but it still needs to be dirtied. This is
-                    // accomplished by pretending they have a height of 1.
-                    logicalBottom = max(logicalBottom, logicalTop + 1);
-                }
-                if (r->m_originatingLine) {
-                    if (!selfNeedsLayout()) {
-                        ASSERT(r->m_originatingLine->renderer() == this);
-                        r->m_originatingLine->markDirty();
-                    }
-#if !ASSERT_DISABLED
-                    r->m_originatingLine = 0;
-#endif
-                }
-                markLinesDirtyInBlockRange(0, logicalBottom);
-            }
-            m_floatingObjects->remove(r);
-            ASSERT(!r->m_originatingLine);
-            delete r;
-        }
-    }
-}
-
-void RenderBlock::removeFloatingObjectsBelow(FloatingObject* lastFloat, int logicalOffset)
+static ContinuationOutlineTableMap* continuationOutlineTable()
 {
-    if (!containsFloats())
-        return;
-    
-    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    FloatingObject* curr = floatingObjectSet.last();
-    while (curr != lastFloat && (!curr->isPlaced() || logicalTopForFloat(curr) >= logicalOffset)) {
-        m_floatingObjects->remove(curr);
-        ASSERT(!curr->m_originatingLine);
-        delete curr;
-        if (floatingObjectSet.isEmpty())
-            break;
-        curr = floatingObjectSet.last();
-    }
+    static NeverDestroyed<ContinuationOutlineTableMap> table;
+    return &table.get();
 }
 
-LayoutPoint RenderBlock::computeLogicalLocationForFloat(const FloatingObject* floatingObject, LayoutUnit logicalTopOffset) const
+void RenderBlock::addContinuationWithOutline(RenderInline* flow)
 {
-    RenderBox* childBox = floatingObject->renderer();
-    LayoutUnit logicalLeftOffset = logicalLeftOffsetForContent(logicalTopOffset); // Constant part of left offset.
-    LayoutUnit logicalRightOffset; // Constant part of right offset.
-#if ENABLE(CSS_SHAPES)
-    // FIXME Bug 102948: This only works for shape outside directly set on this block.
-    ShapeInsideInfo* shapeInsideInfo = this->shapeInsideInfo();
-    // FIXME Bug 102846: Take into account the height of the content. The offset should be
-    // equal to the maximum segment length.
-    if (shapeInsideInfo && shapeInsideInfo->hasSegments() && shapeInsideInfo->segments().size() == 1) {
-        // FIXME Bug 102949: Add support for shapes with multipe segments.
-
-        // The segment offsets are relative to the content box.
-        logicalRightOffset = logicalLeftOffset + shapeInsideInfo->segments()[0].logicalRight;
-        logicalLeftOffset += shapeInsideInfo->segments()[0].logicalLeft;
-    } else
-#endif
-        logicalRightOffset = logicalRightOffsetForContent(logicalTopOffset);
-
-    LayoutUnit floatLogicalWidth = min(logicalWidthForFloat(floatingObject), logicalRightOffset - logicalLeftOffset); // The width we look for.
-
-    LayoutUnit floatLogicalLeft;
-
-    bool insideFlowThread = flowThreadContainingBlock();
-
-    if (childBox->style()->floating() == LeftFloat) {
-        LayoutUnit heightRemainingLeft = 1;
-        LayoutUnit heightRemainingRight = 1;
-        floatLogicalLeft = logicalLeftOffsetForLineIgnoringShapeOutside(logicalTopOffset, logicalLeftOffset, false, &heightRemainingLeft);
-        while (logicalRightOffsetForLineIgnoringShapeOutside(logicalTopOffset, logicalRightOffset, false, &heightRemainingRight) - floatLogicalLeft < floatLogicalWidth) {
-            logicalTopOffset += min(heightRemainingLeft, heightRemainingRight);
-            floatLogicalLeft = logicalLeftOffsetForLineIgnoringShapeOutside(logicalTopOffset, logicalLeftOffset, false, &heightRemainingLeft);
-            if (insideFlowThread) {
-                // Have to re-evaluate all of our offsets, since they may have changed.
-                logicalRightOffset = logicalRightOffsetForContent(logicalTopOffset); // Constant part of right offset.
-                logicalLeftOffset = logicalLeftOffsetForContent(logicalTopOffset); // Constant part of left offset.
-                floatLogicalWidth = min(logicalWidthForFloat(floatingObject), logicalRightOffset - logicalLeftOffset);
-            }
-        }
-        floatLogicalLeft = max(logicalLeftOffset - borderAndPaddingLogicalLeft(), floatLogicalLeft);
-    } else {
-        LayoutUnit heightRemainingLeft = 1;
-        LayoutUnit heightRemainingRight = 1;
-        floatLogicalLeft = logicalRightOffsetForLineIgnoringShapeOutside(logicalTopOffset, logicalRightOffset, false, &heightRemainingRight);
-        while (floatLogicalLeft - logicalLeftOffsetForLineIgnoringShapeOutside(logicalTopOffset, logicalLeftOffset, false, &heightRemainingLeft) < floatLogicalWidth) {
-            logicalTopOffset += min(heightRemainingLeft, heightRemainingRight);
-            floatLogicalLeft = logicalRightOffsetForLineIgnoringShapeOutside(logicalTopOffset, logicalRightOffset, false, &heightRemainingRight);
-            if (insideFlowThread) {
-                // Have to re-evaluate all of our offsets, since they may have changed.
-                logicalRightOffset = logicalRightOffsetForContent(logicalTopOffset); // Constant part of right offset.
-                logicalLeftOffset = logicalLeftOffsetForContent(logicalTopOffset); // Constant part of left offset.
-                floatLogicalWidth = min(logicalWidthForFloat(floatingObject), logicalRightOffset - logicalLeftOffset);
-            }
-        }
-        floatLogicalLeft -= logicalWidthForFloat(floatingObject); // Use the original width of the float here, since the local variable
-                                                                  // |floatLogicalWidth| was capped to the available line width.
-                                                                  // See fast/block/float/clamped-right-float.html.
-    }
+    // We can't make this work if the inline is in a layer.  We'll just rely on the broken
+    // way of painting.
+    ASSERT(!flow->layer() && !flow->isInlineElementContinuation());
     
-    return LayoutPoint(floatLogicalLeft, logicalTopOffset);
-}
-
-bool RenderBlock::positionNewFloats()
-{
-    if (!m_floatingObjects)
-        return false;
-
-    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    if (floatingObjectSet.isEmpty())
-        return false;
-
-    // If all floats have already been positioned, then we have no work to do.
-    if (floatingObjectSet.last()->isPlaced())
-        return false;
-
-    // Move backwards through our floating object list until we find a float that has
-    // already been positioned.  Then we'll be able to move forward, positioning all of
-    // the new floats that need it.
-    FloatingObjectSetIterator it = floatingObjectSet.end();
-    --it; // Go to last item.
-    FloatingObjectSetIterator begin = floatingObjectSet.begin();
-    FloatingObject* lastPlacedFloatingObject = 0;
-    while (it != begin) {
-        --it;
-        if ((*it)->isPlaced()) {
-            lastPlacedFloatingObject = *it;
-            ++it;
-            break;
-        }
+    ContinuationOutlineTableMap* table = continuationOutlineTable();
+    ListHashSet<RenderInline*>* continuations = table->get(this);
+    if (!continuations) {
+        continuations = new ListHashSet<RenderInline*>;
+        table->set(this, std::unique_ptr<ListHashSet<RenderInline*>>(continuations));
     }
-
-    LayoutUnit logicalTop = logicalHeight();
     
-    // The float cannot start above the top position of the last positioned float.
-    if (lastPlacedFloatingObject)
-        logicalTop = max(logicalTopForFloat(lastPlacedFloatingObject), logicalTop);
-
-    FloatingObjectSetIterator end = floatingObjectSet.end();
-    // Now walk through the set of unpositioned floats and place them.
-    for (; it != end; ++it) {
-        FloatingObject* floatingObject = *it;
-        // The containing block is responsible for positioning floats, so if we have floats in our
-        // list that come from somewhere else, do not attempt to position them.
-        if (floatingObject->renderer()->containingBlock() != this)
-            continue;
-
-        RenderBox* childBox = floatingObject->renderer();
-        LayoutUnit childLogicalLeftMargin = style()->isLeftToRightDirection() ? marginStartForChild(childBox) : marginEndForChild(childBox);
-
-        LayoutRect oldRect = childBox->frameRect();
-
-        if (childBox->style()->clear() & CLEFT)
-            logicalTop = max(lowestFloatLogicalBottom(FloatingObject::FloatLeft), logicalTop);
-        if (childBox->style()->clear() & CRIGHT)
-            logicalTop = max(lowestFloatLogicalBottom(FloatingObject::FloatRight), logicalTop);
-
-        LayoutPoint floatLogicalLocation = computeLogicalLocationForFloat(floatingObject, logicalTop);
-
-        setLogicalLeftForFloat(floatingObject, floatLogicalLocation.x());
-
-        setLogicalLeftForChild(childBox, floatLogicalLocation.x() + childLogicalLeftMargin);
-        setLogicalTopForChild(childBox, floatLogicalLocation.y() + marginBeforeForChild(childBox));
-
-        LayoutState* layoutState = view()->layoutState();
-        bool isPaginated = layoutState->isPaginated();
-        if (isPaginated && !childBox->needsLayout())
-            childBox->markForPaginationRelayoutIfNeeded();
-        
-        childBox->layoutIfNeeded();
-
-        if (isPaginated) {
-            // If we are unsplittable and don't fit, then we need to move down.
-            // We include our margins as part of the unsplittable area.
-            LayoutUnit newLogicalTop = adjustForUnsplittableChild(childBox, floatLogicalLocation.y(), true);
-            
-            // See if we have a pagination strut that is making us move down further.
-            // Note that an unsplittable child can't also have a pagination strut, so this is
-            // exclusive with the case above.
-            RenderBlock* childBlock = childBox->isRenderBlock() ? toRenderBlock(childBox) : 0;
-            if (childBlock && childBlock->paginationStrut()) {
-                newLogicalTop += childBlock->paginationStrut();
-                childBlock->setPaginationStrut(0);
-            }
-            
-            if (newLogicalTop != floatLogicalLocation.y()) {
-                floatingObject->m_paginationStrut = newLogicalTop - floatLogicalLocation.y();
-
-                floatLogicalLocation = computeLogicalLocationForFloat(floatingObject, newLogicalTop);
-                setLogicalLeftForFloat(floatingObject, floatLogicalLocation.x());
-
-                setLogicalLeftForChild(childBox, floatLogicalLocation.x() + childLogicalLeftMargin);
-                setLogicalTopForChild(childBox, floatLogicalLocation.y() + marginBeforeForChild(childBox));
-        
-                if (childBlock)
-                    childBlock->setChildNeedsLayout(true, MarkOnlyThis);
-                childBox->layoutIfNeeded();
-            }
-        }
-
-        setLogicalTopForFloat(floatingObject, floatLogicalLocation.y());
-
-        setLogicalHeightForFloat(floatingObject, logicalHeightForChild(childBox) + marginBeforeForChild(childBox) + marginAfterForChild(childBox));
-
-        m_floatingObjects->addPlacedObject(floatingObject);
-
-        // If the child moved, we have to repaint it.
-        if (childBox->checkForRepaintDuringLayout())
-            childBox->repaintDuringLayoutIfMoved(oldRect);
-    }
-    return true;
-}
-
-void RenderBlock::newLine(EClear clear)
-{
-    positionNewFloats();
-    // set y position
-    LayoutUnit newY = 0;
-    switch (clear)
-    {
-        case CLEFT:
-            newY = lowestFloatLogicalBottom(FloatingObject::FloatLeft);
-            break;
-        case CRIGHT:
-            newY = lowestFloatLogicalBottom(FloatingObject::FloatRight);
-            break;
-        case CBOTH:
-            newY = lowestFloatLogicalBottom();
-        default:
-            break;
-    }
-    if (height() < newY)
-        setLogicalHeight(newY);
-}
-
-void RenderBlock::addPercentHeightDescendant(RenderBox* descendant)
-{
-    insertIntoTrackedRendererMaps(descendant, gPercentHeightDescendantsMap, gPercentHeightContainerMap);
-}
-
-void RenderBlock::removePercentHeightDescendant(RenderBox* descendant)
-{
-    removeFromTrackedRendererMaps(descendant, gPercentHeightDescendantsMap, gPercentHeightContainerMap);
-}
-
-TrackedRendererListHashSet* RenderBlock::percentHeightDescendants() const
-{
-    return gPercentHeightDescendantsMap ? gPercentHeightDescendantsMap->get(this) : 0;
-}
-
-bool RenderBlock::hasPercentHeightContainerMap()
-{
-    return gPercentHeightContainerMap;
-}
-
-bool RenderBlock::hasPercentHeightDescendant(RenderBox* descendant)
-{
-    // We don't null check gPercentHeightContainerMap since the caller
-    // already ensures this and we need to call this function on every
-    // descendant in clearPercentHeightDescendantsFrom().
-    ASSERT(gPercentHeightContainerMap);
-    return gPercentHeightContainerMap->contains(descendant);
-}
-
-void RenderBlock::removePercentHeightDescendantIfNeeded(RenderBox* descendant)
-{
-    // We query the map directly, rather than looking at style's
-    // logicalHeight()/logicalMinHeight()/logicalMaxHeight() since those
-    // can change with writing mode/directional changes.
-    if (!hasPercentHeightContainerMap())
-        return;
-
-    if (!hasPercentHeightDescendant(descendant))
-        return;
-
-    removePercentHeightDescendant(descendant);
-}
-
-void RenderBlock::clearPercentHeightDescendantsFrom(RenderBox* parent)
-{
-    ASSERT(gPercentHeightContainerMap);
-    for (RenderObject* curr = parent->firstChild(); curr; curr = curr->nextInPreOrder(parent)) {
-        if (!curr->isBox())
-            continue;
- 
-        RenderBox* box = toRenderBox(curr);
-        if (!hasPercentHeightDescendant(box))
-            continue;
-
-        removePercentHeightDescendant(box);
-    }
-}
-
-static bool rangesIntersect(int floatTop, int floatBottom, int objectTop, int objectBottom)
-{
-    if (objectTop >= floatBottom || objectBottom < floatTop)
-        return false;
-
-    // The top of the object overlaps the float
-    if (objectTop >= floatTop)
-        return true;
-
-    // The object encloses the float
-    if (objectTop < floatTop && objectBottom > floatBottom)
-        return true;
-
-    // The bottom of the object overlaps the float
-    if (objectBottom > objectTop && objectBottom > floatTop && objectBottom <= floatBottom)
-        return true;
-
-    return false;
+    continuations->add(flow);
 }
 
-template <RenderBlock::FloatingObject::Type FloatTypeValue>
-inline void RenderBlock::FloatIntervalSearchAdapter<FloatTypeValue>::collectIfNeeded(const IntervalType& interval) const
+bool RenderBlock::paintsContinuationOutline(RenderInline* flow)
 {
-    const FloatingObject* r = interval.data();
-    if (r->type() != FloatTypeValue || !rangesIntersect(interval.low(), interval.high(), m_lowValue, m_highValue))
-        return;
-
-    // All the objects returned from the tree should be already placed.
-    ASSERT(r->isPlaced() && rangesIntersect(m_renderer->logicalTopForFloat(r), m_renderer->logicalBottomForFloat(r), m_lowValue, m_highValue));
-
-    if (FloatTypeValue == FloatingObject::FloatLeft 
-        && m_renderer->logicalRightForFloat(r) > m_offset) {
-        m_offset = m_renderer->logicalRightForFloat(r);
-        if (m_heightRemaining)
-            *m_heightRemaining = m_renderer->logicalBottomForFloat(r) - m_lowValue;
-    }
-
-    if (FloatTypeValue == FloatingObject::FloatRight
-        && m_renderer->logicalLeftForFloat(r) < m_offset) {
-        m_offset = m_renderer->logicalLeftForFloat(r);
-        if (m_heightRemaining)
-            *m_heightRemaining = m_renderer->logicalBottomForFloat(r) - m_lowValue;
-    }
+    ContinuationOutlineTableMap* table = continuationOutlineTable();
+    if (table->isEmpty())
+        return false;
+        
+    ListHashSet<RenderInline*>* continuations = table->get(this);
+    if (!continuations)
+        return false;
 
-#if ENABLE(CSS_SHAPES)
-    m_last = r;
-#endif
+    return continuations->contains(flow);
 }
 
-LayoutUnit RenderBlock::textIndentOffset() const
+void RenderBlock::paintContinuationOutlines(PaintInfo& info, const LayoutPoint& paintOffset)
 {
-    LayoutUnit cw = 0;
-    RenderView* renderView = 0;
-    if (style()->textIndent().isPercent())
-        cw = containingBlock()->availableLogicalWidth();
-    else if (style()->textIndent().isViewportPercentage())
-        renderView = view();
-    return minimumValueForLength(style()->textIndent(), cw, renderView);
-}
+    ContinuationOutlineTableMap* table = continuationOutlineTable();
+    if (table->isEmpty())
+        return;
+        
+    std::unique_ptr<ListHashSet<RenderInline*>> continuations = table->take(this);
+    if (!continuations)
+        return;
 
-LayoutUnit RenderBlock::logicalLeftOffsetForContent(RenderRegion* region) const
-{
-    LayoutUnit logicalLeftOffset = style()->isHorizontalWritingMode() ? borderLeft() + paddingLeft() : borderTop() + paddingTop();
-    if (!region)
-        return logicalLeftOffset;
-    LayoutRect boxRect = borderBoxRectInRegion(region);
-    return logicalLeftOffset + (isHorizontalWritingMode() ? boxRect.x() : boxRect.y());
+    LayoutPoint accumulatedPaintOffset = paintOffset;
+    // Paint each continuation outline.
+    ListHashSet<RenderInline*>::iterator end = continuations->end();
+    for (ListHashSet<RenderInline*>::iterator it = continuations->begin(); it != end; ++it) {
+        // Need to add in the coordinates of the intervening blocks.
+        RenderInline* flow = *it;
+        RenderBlock* block = flow->containingBlock();
+        for ( ; block && block != this; block = block->containingBlock())
+            accumulatedPaintOffset.moveBy(block->location());
+        ASSERT(block);   
+        flow->paintOutline(info, accumulatedPaintOffset);
+    }
 }
 
-LayoutUnit RenderBlock::logicalRightOffsetForContent(RenderRegion* region) const
+bool RenderBlock::shouldPaintSelectionGaps() const
 {
-    LayoutUnit logicalRightOffset = style()->isHorizontalWritingMode() ? borderLeft() + paddingLeft() : borderTop() + paddingTop();
-    logicalRightOffset += availableLogicalWidth();
-    if (!region)
-        return logicalRightOffset;
-    LayoutRect boxRect = borderBoxRectInRegion(region);
-    return logicalRightOffset - (logicalWidth() - (isHorizontalWritingMode() ? boxRect.maxX() : boxRect.maxY()));
+    return selectionState() != SelectionNone && style().visibility() == VISIBLE && isSelectionRoot();
 }
 
-LayoutUnit RenderBlock::logicalLeftFloatOffsetForLine(LayoutUnit logicalTop, LayoutUnit fixedOffset, LayoutUnit* heightRemaining, LayoutUnit logicalHeight, ShapeOutsideFloatOffsetMode offsetMode) const
+bool RenderBlock::isSelectionRoot() const
 {
-#if !ENABLE(CSS_SHAPES)
-    UNUSED_PARAM(offsetMode);
-#endif
-    LayoutUnit left = fixedOffset;
-    if (m_floatingObjects && m_floatingObjects->hasLeftObjects()) {
-        if (heightRemaining)
-            *heightRemaining = 1;
-
-        FloatIntervalSearchAdapter<FloatingObject::FloatLeft> adapter(this, roundToInt(logicalTop), roundToInt(logicalTop + logicalHeight), left, heightRemaining);
-        m_floatingObjects->placedFloatsTree().allOverlapsWithAdapter(adapter);
-
-#if ENABLE(CSS_SHAPES)
-        const FloatingObject* lastFloat = adapter.lastFloat();
-        if (offsetMode == ShapeOutsideFloatShapeOffset && lastFloat) {
-            if (ShapeOutsideInfo* shapeOutside = lastFloat->renderer()->shapeOutsideInfo()) {
-                shapeOutside->computeSegmentsForContainingBlockLine(logicalTop, logicalTopForFloat(lastFloat), logicalHeight);
-                left += shapeOutside->rightSegmentMarginBoxDelta();
-            }
-        }
-#endif
+    if (isPseudoElement())
+        return false;
+    ASSERT(element() || isAnonymous());
+        
+    // FIXME: Eventually tables should have to learn how to fill gaps between cells, at least in simple non-spanning cases.
+    if (isTable())
+        return false;
+        
+    if (isBody() || isDocumentElementRenderer() || hasOverflowClip()
+        || isPositioned() || isFloating()
+        || isTableCell() || isInlineBlockOrInlineTable()
+        || hasTransform() || hasReflection() || hasMask() || isWritingModeRoot()
+        || isRenderFlowThread() || style().columnSpan() == ColumnSpanAll)
+        return true;
+    
+    if (view().selectionUnsplitStart()) {
+        Node* startElement = view().selectionUnsplitStart()->node();
+        if (startElement && startElement->rootEditableElement() == element())
+            return true;
     }
-
-    return left;
+    
+    return false;
 }
 
-LayoutUnit RenderBlock::adjustLogicalLeftOffsetForLine(LayoutUnit offsetFromFloats, bool applyTextIndent) const
+GapRects RenderBlock::selectionGapRectsForRepaint(const RenderLayerModelObject* repaintContainer)
 {
-    LayoutUnit left = offsetFromFloats;
-
-    if (applyTextIndent && style()->isLeftToRightDirection())
-        left += textIndentOffset();
-
-    if (style()->lineAlign() == LineAlignNone)
-        return left;
-    
-    // Push in our left offset so that it is aligned with the character grid.
-    LayoutState* layoutState = view()->layoutState();
-    if (!layoutState)
-        return left;
+    ASSERT(!needsLayout());
 
-    RenderBlock* lineGrid = layoutState->lineGrid();
-    if (!lineGrid || lineGrid->style()->writingMode() != style()->writingMode())
-        return left;
+    if (!shouldPaintSelectionGaps())
+        return GapRects();
 
-    // FIXME: Should letter-spacing apply? This is complicated since it doesn't apply at the edge?
-    float maxCharWidth = lineGrid->style()->font().primaryFont()->maxCharWidth();
-    if (!maxCharWidth)
-        return left;
+    FloatPoint containerPoint = localToContainerPoint(FloatPoint(), repaintContainer, UseTransforms);
+    LayoutPoint offsetFromRepaintContainer(containerPoint - scrolledContentOffset());
 
-    LayoutUnit lineGridOffset = lineGrid->isHorizontalWritingMode() ? layoutState->lineGridOffset().width(): layoutState->lineGridOffset().height();
-    LayoutUnit layoutOffset = lineGrid->isHorizontalWritingMode() ? layoutState->layoutOffset().width() : layoutState->layoutOffset().height();
+    LogicalSelectionOffsetCaches cache(*this);
+    LayoutUnit lastTop = 0;
+    LayoutUnit lastLeft = logicalLeftSelectionOffset(*this, lastTop, cache);
+    LayoutUnit lastRight = logicalRightSelectionOffset(*this, lastTop, cache);
     
-    // Push in to the nearest character width (truncated so that we pixel snap left).
-    // FIXME: Should be patched when subpixel layout lands, since this calculation doesn't have to pixel snap
-    // any more (https://bugs.webkit.org/show_bug.cgi?id=79946).
-    // FIXME: This is wrong for RTL (https://bugs.webkit.org/show_bug.cgi?id=79945).
-    // FIXME: This doesn't work with columns or regions (https://bugs.webkit.org/show_bug.cgi?id=79942).
-    // FIXME: This doesn't work when the inline position of the object isn't set ahead of time.
-    // FIXME: Dynamic changes to the font or to the inline position need to result in a deep relayout.
-    // (https://bugs.webkit.org/show_bug.cgi?id=79944)
-    float remainder = fmodf(maxCharWidth - fmodf(left + layoutOffset - lineGridOffset, maxCharWidth), maxCharWidth);
-    left += remainder;
-    return left;
+    return selectionGaps(*this, offsetFromRepaintContainer, IntSize(), lastTop, lastLeft, lastRight, cache);
 }
 
-LayoutUnit RenderBlock::logicalRightFloatOffsetForLine(LayoutUnit logicalTop, LayoutUnit fixedOffset, LayoutUnit* heightRemaining, LayoutUnit logicalHeight, ShapeOutsideFloatOffsetMode offsetMode) const
+void RenderBlock::paintSelection(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
-#if !ENABLE(CSS_SHAPES)
-    UNUSED_PARAM(offsetMode);
-#endif
-    LayoutUnit right = fixedOffset;
-    if (m_floatingObjects && m_floatingObjects->hasRightObjects()) {
-        if (heightRemaining)
-            *heightRemaining = 1;
-
-        LayoutUnit rightFloatOffset = fixedOffset;
-        FloatIntervalSearchAdapter<FloatingObject::FloatRight> adapter(this, roundToInt(logicalTop), roundToInt(logicalTop + logicalHeight), rightFloatOffset, heightRemaining);
-        m_floatingObjects->placedFloatsTree().allOverlapsWithAdapter(adapter);
+#if ENABLE(TEXT_SELECTION)
+    if (shouldPaintSelectionGaps() && paintInfo.phase == PaintPhaseForeground) {
+        LogicalSelectionOffsetCaches cache(*this);
+        LayoutUnit lastTop = 0;
+        LayoutUnit lastLeft = logicalLeftSelectionOffset(*this, lastTop, cache);
+        LayoutUnit lastRight = logicalRightSelectionOffset(*this, lastTop, cache);
+        GraphicsContextStateSaver stateSaver(paintInfo.context());
 
-#if ENABLE(CSS_SHAPES)
-        const FloatingObject* lastFloat = adapter.lastFloat();
-        if (offsetMode == ShapeOutsideFloatShapeOffset && lastFloat) {
-            if (ShapeOutsideInfo* shapeOutside = lastFloat->renderer()->shapeOutsideInfo()) {
-                shapeOutside->computeSegmentsForContainingBlockLine(logicalTop, logicalTopForFloat(lastFloat), logicalHeight);
-                rightFloatOffset += shapeOutside->leftSegmentMarginBoxDelta();
+        LayoutRect gapRectsBounds = selectionGaps(*this, paintOffset, LayoutSize(), lastTop, lastLeft, lastRight, cache, &paintInfo);
+        if (!gapRectsBounds.isEmpty()) {
+            if (RenderLayer* layer = enclosingLayer()) {
+                gapRectsBounds.moveBy(-paintOffset);
+                if (!hasLayer()) {
+                    LayoutRect localBounds(gapRectsBounds);
+                    flipForWritingMode(localBounds);
+                    gapRectsBounds = localToContainerQuad(FloatRect(localBounds), &layer->renderer()).enclosingBoundingBox();
+                    if (layer->renderer().isBox())
+                        gapRectsBounds.move(layer->renderBox()->scrolledContentOffset());
+                }
+                layer->addBlockSelectionGapsBounds(gapRectsBounds);
             }
         }
-#endif
-
-        right = min(right, rightFloatOffset);
     }
-
-    return right;
+#else
+    UNUSED_PARAM(paintInfo);
+    UNUSED_PARAM(paintOffset);
+#endif
 }
 
-LayoutUnit RenderBlock::adjustLogicalRightOffsetForLine(LayoutUnit offsetFromFloats, bool applyTextIndent) const
+static void clipOutPositionedObjects(const PaintInfo* paintInfo, const LayoutPoint& offset, TrackedRendererListHashSet* positionedObjects)
 {
-    LayoutUnit right = offsetFromFloats;
-    
-    if (applyTextIndent && !style()->isLeftToRightDirection())
-        right -= textIndentOffset();
-    
-    if (style()->lineAlign() == LineAlignNone)
-        return right;
-    
-    // Push in our right offset so that it is aligned with the character grid.
-    LayoutState* layoutState = view()->layoutState();
-    if (!layoutState)
-        return right;
-
-    RenderBlock* lineGrid = layoutState->lineGrid();
-    if (!lineGrid || lineGrid->style()->writingMode() != style()->writingMode())
-        return right;
-
-    // FIXME: Should letter-spacing apply? This is complicated since it doesn't apply at the edge?
-    float maxCharWidth = lineGrid->style()->font().primaryFont()->maxCharWidth();
-    if (!maxCharWidth)
-        return right;
-
-    LayoutUnit lineGridOffset = lineGrid->isHorizontalWritingMode() ? layoutState->lineGridOffset().width(): layoutState->lineGridOffset().height();
-    LayoutUnit layoutOffset = lineGrid->isHorizontalWritingMode() ? layoutState->layoutOffset().width() : layoutState->layoutOffset().height();
+    if (!positionedObjects)
+        return;
     
-    // Push in to the nearest character width (truncated so that we pixel snap right).
-    // FIXME: Should be patched when subpixel layout lands, since this calculation doesn't have to pixel snap
-    // any more (https://bugs.webkit.org/show_bug.cgi?id=79946).
-    // FIXME: This is wrong for RTL (https://bugs.webkit.org/show_bug.cgi?id=79945).
-    // FIXME: This doesn't work with columns or regions (https://bugs.webkit.org/show_bug.cgi?id=79942).
-    // FIXME: This doesn't work when the inline position of the object isn't set ahead of time.
-    // FIXME: Dynamic changes to the font or to the inline position need to result in a deep relayout.
-    // (https://bugs.webkit.org/show_bug.cgi?id=79944)
-    float remainder = fmodf(fmodf(right + layoutOffset - lineGridOffset, maxCharWidth), maxCharWidth);
-    right -= ceilf(remainder);
-    return right;
+    TrackedRendererListHashSet::const_iterator end = positionedObjects->end();
+    for (TrackedRendererListHashSet::const_iterator it = positionedObjects->begin(); it != end; ++it) {
+        RenderBox* r = *it;
+        paintInfo->context().clipOut(IntRect(offset.x() + r->x(), offset.y() + r->y(), r->width(), r->height()));
+    }
 }
 
-LayoutUnit RenderBlock::nextFloatLogicalBottomBelow(LayoutUnit logicalHeight) const
+LayoutUnit blockDirectionOffset(RenderBlock& rootBlock, const LayoutSize& offsetFromRootBlock)
 {
-    if (!m_floatingObjects)
-        return logicalHeight;
-
-    LayoutUnit bottom = LayoutUnit::max();
-    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    FloatingObjectSetIterator end = floatingObjectSet.end();
-    for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-        FloatingObject* r = *it;
-        LayoutUnit floatBottom = logicalBottomForFloat(r);
-        if (floatBottom > logicalHeight)
-            bottom = min(floatBottom, bottom);
-    }
-
-    return bottom == LayoutUnit::max() ? LayoutUnit() : bottom;
+    return rootBlock.isHorizontalWritingMode() ? offsetFromRootBlock.height() : offsetFromRootBlock.width();
 }
 
-LayoutUnit RenderBlock::lowestFloatLogicalBottom(FloatingObject::Type floatType) const
+LayoutUnit inlineDirectionOffset(RenderBlock& rootBlock, const LayoutSize& offsetFromRootBlock)
 {
-    if (!m_floatingObjects)
-        return 0;
-    LayoutUnit lowestFloatBottom = 0;
-    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    FloatingObjectSetIterator end = floatingObjectSet.end();
-    for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-        FloatingObject* r = *it;
-        if (r->isPlaced() && r->type() & floatType)
-            lowestFloatBottom = max(lowestFloatBottom, logicalBottomForFloat(r));
-    }
-    return lowestFloatBottom;
+    return rootBlock.isHorizontalWritingMode() ? offsetFromRootBlock.width() : offsetFromRootBlock.height();
 }
 
-void RenderBlock::markLinesDirtyInBlockRange(LayoutUnit logicalTop, LayoutUnit logicalBottom, RootInlineBox* highest)
+LayoutRect RenderBlock::logicalRectToPhysicalRect(const LayoutPoint& rootBlockPhysicalPosition, const LayoutRect& logicalRect)
 {
-    if (logicalTop >= logicalBottom)
-        return;
-
-    RootInlineBox* lowestDirtyLine = lastRootBox();
-    RootInlineBox* afterLowest = lowestDirtyLine;
-    while (lowestDirtyLine && lowestDirtyLine->lineBottomWithLeading() >= logicalBottom && logicalBottom < LayoutUnit::max()) {
-        afterLowest = lowestDirtyLine;
-        lowestDirtyLine = lowestDirtyLine->prevRootBox();
-    }
-
-    while (afterLowest && afterLowest != highest && (afterLowest->lineBottomWithLeading() >= logicalTop || afterLowest->lineBottomWithLeading() < 0)) {
-        afterLowest->markDirty();
-        afterLowest = afterLowest->prevRootBox();
-    }
+    LayoutRect result;
+    if (isHorizontalWritingMode())
+        result = logicalRect;
+    else
+        result = LayoutRect(logicalRect.y(), logicalRect.x(), logicalRect.height(), logicalRect.width());
+    flipForWritingMode(result);
+    result.moveBy(rootBlockPhysicalPosition);
+    return result;
 }
 
-void RenderBlock::clearFloats()
+GapRects RenderBlock::selectionGaps(RenderBlock& rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
+    LayoutUnit& lastLogicalTop, LayoutUnit& lastLogicalLeft, LayoutUnit& lastLogicalRight, const LogicalSelectionOffsetCaches& cache, const PaintInfo* paintInfo)
 {
-    if (m_floatingObjects)
-        m_floatingObjects->setHorizontalWritingMode(isHorizontalWritingMode());
-
-    HashSet<RenderBox*> oldIntrudingFloatSet;
-    if (!childrenInline() && m_floatingObjects) {
-        const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-        FloatingObjectSetIterator end = floatingObjectSet.end();
-        for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-            FloatingObject* floatingObject = *it;
-            if (!floatingObject->isDescendant())
-                oldIntrudingFloatSet.add(floatingObject->m_renderer);
+    // IMPORTANT: Callers of this method that intend for painting to happen need to do a save/restore.
+    // Clip out floating and positioned objects when painting selection gaps.
+    if (paintInfo) {
+        // Note that we don't clip out overflow for positioned objects.  We just stick to the border box.
+        LayoutRect flippedBlockRect(offsetFromRootBlock.width(), offsetFromRootBlock.height(), width(), height());
+        rootBlock.flipForWritingMode(flippedBlockRect);
+        flippedBlockRect.moveBy(rootBlockPhysicalPosition);
+        clipOutPositionedObjects(paintInfo, flippedBlockRect.location(), positionedObjects());
+        if (isBody() || isDocumentElementRenderer()) { // The <body> must make sure to examine its containingBlock's positioned objects.
+            for (RenderBlock* cb = containingBlock(); cb && !is<RenderView>(*cb); cb = cb->containingBlock())
+                clipOutPositionedObjects(paintInfo, LayoutPoint(cb->x(), cb->y()), cb->positionedObjects()); // FIXME: Not right for flipped writing modes.
         }
+        clipOutFloatingObjects(rootBlock, paintInfo, rootBlockPhysicalPosition, offsetFromRootBlock);
     }
 
-    // Inline blocks are covered by the isReplaced() check in the avoidFloats method.
-    if (avoidsFloats() || isRoot() || isRenderView() || isFloatingOrOutOfFlowPositioned() || isTableCell()) {
-        if (m_floatingObjects) {
-            deleteAllValues(m_floatingObjects->set());
-            m_floatingObjects->clear();
-        }
-        if (!oldIntrudingFloatSet.isEmpty())
-            markAllDescendantsWithFloatsForLayout();
-        return;
+    // FIXME: overflow: auto/scroll regions need more math here, since painting in the border box is different from painting in the padding box (one is scrolled, the other is
+    // fixed).
+    GapRects result;
+    if (!isRenderBlockFlow()) // FIXME: Make multi-column selection gap filling work someday.
+        return result;
+
+    if (hasTransform() || style().columnSpan() == ColumnSpanAll || isInFlowRenderFlowThread()) {
+        // FIXME: We should learn how to gap fill multiple columns and transforms eventually.
+        lastLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalHeight();
+        lastLogicalLeft = logicalLeftSelectionOffset(rootBlock, logicalHeight(), cache);
+        lastLogicalRight = logicalRightSelectionOffset(rootBlock, logicalHeight(), cache);
+        return result;
+    }
+    
+    RenderNamedFlowFragment* namedFlowFragment = currentRenderNamedFlowFragment();
+    if (paintInfo && namedFlowFragment && is<RenderFlowThread>(*paintInfo->paintContainer)) {
+        // Make sure the current object is actually flowed into the region being painted.
+        if (!downcast<RenderFlowThread>(*paintInfo->paintContainer).objectShouldFragmentInFlowRegion(this, namedFlowFragment))
+            return result;
     }
 
-    typedef HashMap<RenderObject*, FloatingObject*> RendererToFloatInfoMap;
-    RendererToFloatInfoMap floatMap;
+    if (childrenInline())
+        result = inlineSelectionGaps(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, lastLogicalTop, lastLogicalLeft, lastLogicalRight, cache, paintInfo);
+    else
+        result = blockSelectionGaps(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, lastLogicalTop, lastLogicalLeft, lastLogicalRight, cache, paintInfo);
 
-    if (m_floatingObjects) {
-        const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-        if (childrenInline()) {
-            FloatingObjectSetIterator end = floatingObjectSet.end();
-            for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-                FloatingObject* f = *it;
-                floatMap.add(f->m_renderer, f);
-            }
-        } else
-            deleteAllValues(floatingObjectSet);
-        m_floatingObjects->clear();
+    // Fill the vertical gap all the way to the bottom of our block if the selection extends past our block.
+    if (&rootBlock == this && (selectionState() != SelectionBoth && selectionState() != SelectionEnd) && !isRubyBase() && !isRubyText()) {
+        result.uniteCenter(blockSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock,
+            lastLogicalTop, lastLogicalLeft, lastLogicalRight, logicalHeight(), cache, paintInfo));
     }
 
-    // We should not process floats if the parent node is not a RenderBlock. Otherwise, we will add 
-    // floats in an invalid context. This will cause a crash arising from a bad cast on the parent.
-    // See <rdar://problem/8049753>, where float property is applied on a text node in a SVG.
-    if (!parent() || !parent()->isRenderBlock())
-        return;
+    return result;
+}
 
-    // Attempt to locate a previous sibling with overhanging floats.  We skip any elements that are
-    // out of flow (like floating/positioned elements), and we also skip over any objects that may have shifted
-    // to avoid floats.
-    RenderBlock* parentBlock = toRenderBlock(parent());
-    bool parentHasFloats = false;
-    RenderObject* prev = previousSibling();
-    while (prev && (prev->isFloatingOrOutOfFlowPositioned() || !prev->isBox() || !prev->isRenderBlock() || toRenderBlock(prev)->avoidsFloats())) {
-        if (prev->isFloating())
-            parentHasFloats = true;
-        prev = prev->previousSibling();
-    }
+GapRects RenderBlock::inlineSelectionGaps(RenderBlock&, const LayoutPoint&, const LayoutSize&, LayoutUnit&, LayoutUnit&, LayoutUnit&, const LogicalSelectionOffsetCaches&, const PaintInfo*)
+{
+    ASSERT_NOT_REACHED();
+    return GapRects();
+}
+
+GapRects RenderBlock::blockSelectionGaps(RenderBlock& rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
+    LayoutUnit& lastLogicalTop, LayoutUnit& lastLogicalLeft, LayoutUnit& lastLogicalRight, const LogicalSelectionOffsetCaches& cache, const PaintInfo* paintInfo)
+{
+    GapRects result;
 
-    // First add in floats from the parent.
-    LayoutUnit logicalTopOffset = logicalTop();
-    if (parentHasFloats)
-        addIntrudingFloats(parentBlock, parentBlock->logicalLeftOffsetForContent(), logicalTopOffset);
+    // Jump right to the first block child that contains some selected objects.
+    RenderBox* curr;
+    for (curr = firstChildBox(); curr && curr->selectionState() == SelectionNone; curr = curr->nextSiblingBox()) { }
     
-    LayoutUnit logicalLeftOffset = 0;
-    if (prev)
-        logicalTopOffset -= toRenderBox(prev)->logicalTop();
-    else {
-        prev = parentBlock;
-        logicalLeftOffset += parentBlock->logicalLeftOffsetForContent();
-    }
+    if (!curr)
+        return result;
 
-    // Add overhanging floats from the previous RenderBlock, but only if it has a float that intrudes into our space.    
-    RenderBlock* block = toRenderBlock(prev);
-    if (block->m_floatingObjects && block->lowestFloatLogicalBottom() > logicalTopOffset)
-        addIntrudingFloats(block, logicalLeftOffset, logicalTopOffset);
+    LogicalSelectionOffsetCaches childCache(*this, cache);
 
-    if (childrenInline()) {
-        LayoutUnit changeLogicalTop = LayoutUnit::max();
-        LayoutUnit changeLogicalBottom = LayoutUnit::min();
-        if (m_floatingObjects) {
-            const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-            FloatingObjectSetIterator end = floatingObjectSet.end();
-            for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-                FloatingObject* f = *it;
-                FloatingObject* oldFloatingObject = floatMap.get(f->m_renderer);
-                LayoutUnit logicalBottom = logicalBottomForFloat(f);
-                if (oldFloatingObject) {
-                    LayoutUnit oldLogicalBottom = logicalBottomForFloat(oldFloatingObject);
-                    if (logicalWidthForFloat(f) != logicalWidthForFloat(oldFloatingObject) || logicalLeftForFloat(f) != logicalLeftForFloat(oldFloatingObject)) {
-                        changeLogicalTop = 0;
-                        changeLogicalBottom = max(changeLogicalBottom, max(logicalBottom, oldLogicalBottom));
-                    } else {
-                        if (logicalBottom != oldLogicalBottom) {
-                            changeLogicalTop = min(changeLogicalTop, min(logicalBottom, oldLogicalBottom));
-                            changeLogicalBottom = max(changeLogicalBottom, max(logicalBottom, oldLogicalBottom));
-                        }
-                        LayoutUnit logicalTop = logicalTopForFloat(f);
-                        LayoutUnit oldLogicalTop = logicalTopForFloat(oldFloatingObject);
-                        if (logicalTop != oldLogicalTop) {
-                            changeLogicalTop = min(changeLogicalTop, min(logicalTop, oldLogicalTop));
-                            changeLogicalBottom = max(changeLogicalBottom, max(logicalTop, oldLogicalTop));
-                        }
-                    }
-
-                    floatMap.remove(f->m_renderer);
-                    if (oldFloatingObject->m_originatingLine && !selfNeedsLayout()) {
-                        ASSERT(oldFloatingObject->m_originatingLine->renderer() == this);
-                        oldFloatingObject->m_originatingLine->markDirty();
-                    }
-                    delete oldFloatingObject;
-                } else {
-                    changeLogicalTop = 0;
-                    changeLogicalBottom = max(changeLogicalBottom, logicalBottom);
-                }
-            }
+    for (bool sawSelectionEnd = false; curr && !sawSelectionEnd; curr = curr->nextSiblingBox()) {
+        SelectionState childState = curr->selectionState();
+        if (childState == SelectionBoth || childState == SelectionEnd)
+            sawSelectionEnd = true;
+
+        if (curr->isFloatingOrOutOfFlowPositioned())
+            continue; // We must be a normal flow object in order to even be considered.
+
+        if (curr->isInFlowPositioned() && curr->hasLayer()) {
+            // If the relposition offset is anything other than 0, then treat this just like an absolute positioned element.
+            // Just disregard it completely.
+            LayoutSize relOffset = curr->layer()->offsetForInFlowPosition();
+            if (relOffset.width() || relOffset.height())
+                continue;
         }
 
-        RendererToFloatInfoMap::iterator end = floatMap.end();
-        for (RendererToFloatInfoMap::iterator it = floatMap.begin(); it != end; ++it) {
-            FloatingObject* floatingObject = (*it).value;
-            if (!floatingObject->isDescendant()) {
-                changeLogicalTop = 0;
-                changeLogicalBottom = max(changeLogicalBottom, logicalBottomForFloat(floatingObject));
+        bool paintsOwnSelection = curr->shouldPaintSelectionGaps() || curr->isTable(); // FIXME: Eventually we won't special-case table like this.
+        bool fillBlockGaps = (paintsOwnSelection || (curr->canBeSelectionLeaf() && childState != SelectionNone)) && !isRubyBase() && !isRubyText();
+        if (fillBlockGaps) {
+            // We need to fill the vertical gap above this object.
+            if (childState == SelectionEnd || childState == SelectionInside) {
+                // Fill the gap above the object.
+                result.uniteCenter(blockSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock,
+                    lastLogicalTop, lastLogicalLeft, lastLogicalRight, curr->logicalTop(), cache, paintInfo));
             }
-        }
-        deleteAllValues(floatMap);
-
-        markLinesDirtyInBlockRange(changeLogicalTop, changeLogicalBottom);
-    } else if (!oldIntrudingFloatSet.isEmpty()) {
-        // If there are previously intruding floats that no longer intrude, then children with floats
-        // should also get layout because they might need their floating object lists cleared.
-        if (m_floatingObjects->set().size() < oldIntrudingFloatSet.size())
-            markAllDescendantsWithFloatsForLayout();
-        else {
-            const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-            FloatingObjectSetIterator end = floatingObjectSet.end();
-            for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end && !oldIntrudingFloatSet.isEmpty(); ++it)
-                oldIntrudingFloatSet.remove((*it)->m_renderer);
-            if (!oldIntrudingFloatSet.isEmpty())
-                markAllDescendantsWithFloatsForLayout();
-        }
-    }
-}
 
-LayoutUnit RenderBlock::addOverhangingFloats(RenderBlock* child, bool makeChildPaintOtherFloats)
-{
-    // Prevent floats from being added to the canvas by the root element, e.g., <html>.
-    if (child->hasOverflowClip() || !child->containsFloats() || child->isRoot() || child->hasColumns() || child->isWritingModeRoot())
-        return 0;
+            // Only fill side gaps for objects that paint their own selection if we know for sure the selection is going to extend all the way *past*
+            // our object.  We know this if the selection did not end inside our object.
+            if (paintsOwnSelection && (childState == SelectionStart || sawSelectionEnd))
+                childState = SelectionNone;
 
-    LayoutUnit childLogicalTop = child->logicalTop();
-    LayoutUnit childLogicalLeft = child->logicalLeft();
-    LayoutUnit lowestFloatLogicalBottom = 0;
-
-    // Floats that will remain the child's responsibility to paint should factor into its
-    // overflow.
-    FloatingObjectSetIterator childEnd = child->m_floatingObjects->set().end();
-    for (FloatingObjectSetIterator childIt = child->m_floatingObjects->set().begin(); childIt != childEnd; ++childIt) {
-        FloatingObject* r = *childIt;
-        LayoutUnit logicalBottomForFloat = min(this->logicalBottomForFloat(r), LayoutUnit::max() - childLogicalTop);
-        LayoutUnit logicalBottom = childLogicalTop + logicalBottomForFloat;
-        lowestFloatLogicalBottom = max(lowestFloatLogicalBottom, logicalBottom);
-
-        if (logicalBottom > logicalHeight()) {
-            // If the object is not in the list, we add it now.
-            if (!containsFloat(r->m_renderer)) {
-                LayoutSize offset = isHorizontalWritingMode() ? LayoutSize(-childLogicalLeft, -childLogicalTop) : LayoutSize(-childLogicalTop, -childLogicalLeft);
-                FloatingObject* floatingObj = new FloatingObject(r->type(), LayoutRect(r->frameRect().location() - offset, r->frameRect().size()));
-                floatingObj->m_renderer = r->m_renderer;
-
-                // The nearest enclosing layer always paints the float (so that zindex and stacking
-                // behaves properly).  We always want to propagate the desire to paint the float as
-                // far out as we can, to the outermost block that overlaps the float, stopping only
-                // if we hit a self-painting layer boundary.
-                if (r->m_renderer->enclosingFloatPaintingLayer() == enclosingFloatPaintingLayer())
-                    r->setShouldPaint(false);
-                else
-                    floatingObj->setShouldPaint(false);
+            // Fill side gaps on this object based off its state.
+            bool leftGap, rightGap;
+            getSelectionGapInfo(childState, leftGap, rightGap);
 
-                floatingObj->setIsDescendant(true);
+            if (leftGap)
+                result.uniteLeft(logicalLeftSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, this, curr->logicalLeft(), curr->logicalTop(), curr->logicalHeight(), cache, paintInfo));
+            if (rightGap)
+                result.uniteRight(logicalRightSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, this, curr->logicalRight(), curr->logicalTop(), curr->logicalHeight(), cache, paintInfo));
 
-                // We create the floating object list lazily.
-                if (!m_floatingObjects)
-                    createFloatingObjects();
-                m_floatingObjects->add(floatingObj);
-            }
-        } else {
-            if (makeChildPaintOtherFloats && !r->shouldPaint() && !r->m_renderer->hasSelfPaintingLayer()
-                && r->m_renderer->isDescendantOf(child) && r->m_renderer->enclosingFloatPaintingLayer() == child->enclosingFloatPaintingLayer()) {
-                // The float is not overhanging from this block, so if it is a descendant of the child, the child should
-                // paint it (the other case is that it is intruding into the child), unless it has its own layer or enclosing
-                // layer.
-                // If makeChildPaintOtherFloats is false, it means that the child must already know about all the floats
-                // it should paint.
-                r->setShouldPaint(true);
-            }
-            
-            // Since the float doesn't overhang, it didn't get put into our list.  We need to go ahead and add its overflow in to the
-            // child now.
-            if (r->isDescendant())
-                child->addOverflowFromChild(r->m_renderer, LayoutSize(xPositionForFloatIncludingMargin(r), yPositionForFloatIncludingMargin(r)));
+            // Update lastLogicalTop to be just underneath the object.  lastLogicalLeft and lastLogicalRight extend as far as
+            // they can without bumping into floating or positioned objects.  Ideally they will go right up
+            // to the border of the root selection block.
+            lastLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + curr->logicalBottom();
+            lastLogicalLeft = logicalLeftSelectionOffset(rootBlock, curr->logicalBottom(), cache);
+            lastLogicalRight = logicalRightSelectionOffset(rootBlock, curr->logicalBottom(), cache);
+        } else if (childState != SelectionNone && is<RenderBlock>(*curr)) {
+            // We must be a block that has some selected object inside it, so recur.
+            result.unite(downcast<RenderBlock>(*curr).selectionGaps(rootBlock, rootBlockPhysicalPosition, LayoutSize(offsetFromRootBlock.width() + curr->x(), offsetFromRootBlock.height() + curr->y()),
+                lastLogicalTop, lastLogicalLeft, lastLogicalRight, childCache, paintInfo));
         }
     }
-    return lowestFloatLogicalBottom;
+    return result;
 }
 
-bool RenderBlock::hasOverhangingFloat(RenderBox* renderer)
+LayoutRect RenderBlock::blockSelectionGap(RenderBlock& rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
+    LayoutUnit lastLogicalTop, LayoutUnit lastLogicalLeft, LayoutUnit lastLogicalRight, LayoutUnit logicalBottom, const LogicalSelectionOffsetCaches& cache, const PaintInfo* paintInfo)
 {
-    if (!m_floatingObjects || hasColumns() || !parent())
-        return false;
+    LayoutUnit logicalTop = lastLogicalTop;
+    LayoutUnit logicalHeight = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalBottom - logicalTop;
+    if (logicalHeight <= 0)
+        return LayoutRect();
 
-    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    FloatingObjectSetIterator it = floatingObjectSet.find<RenderBox*, FloatingObjectHashTranslator>(renderer);
-    if (it == floatingObjectSet.end())
-        return false;
+    // Get the selection offsets for the bottom of the gap
+    LayoutUnit logicalLeft = std::max(lastLogicalLeft, logicalLeftSelectionOffset(rootBlock, logicalBottom, cache));
+    LayoutUnit logicalRight = std::min(lastLogicalRight, logicalRightSelectionOffset(rootBlock, logicalBottom, cache));
+    LayoutUnit logicalWidth = logicalRight - logicalLeft;
+    if (logicalWidth <= 0)
+        return LayoutRect();
 
-    return logicalBottomForFloat(*it) > logicalHeight();
+    LayoutRect gapRect = rootBlock.logicalRectToPhysicalRect(rootBlockPhysicalPosition, LayoutRect(logicalLeft, logicalTop, logicalWidth, logicalHeight));
+    if (paintInfo)
+        paintInfo->context().fillRect(snapRectToDevicePixels(gapRect, document().deviceScaleFactor()), selectionBackgroundColor());
+    return gapRect;
 }
 
-void RenderBlock::addIntrudingFloats(RenderBlock* prev, LayoutUnit logicalLeftOffset, LayoutUnit logicalTopOffset)
+LayoutRect RenderBlock::logicalLeftSelectionGap(RenderBlock& rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
+    RenderBoxModelObject* selObj, LayoutUnit logicalLeft, LayoutUnit logicalTop, LayoutUnit logicalHeight, const LogicalSelectionOffsetCaches& cache, const PaintInfo* paintInfo)
 {
-    ASSERT(!avoidsFloats());
-
-    // If the parent or previous sibling doesn't have any floats to add, don't bother.
-    if (!prev->m_floatingObjects)
-        return;
+    LayoutUnit rootBlockLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalTop;
+    LayoutUnit rootBlockLogicalLeft = std::max(logicalLeftSelectionOffset(rootBlock, logicalTop, cache), logicalLeftSelectionOffset(rootBlock, logicalTop + logicalHeight, cache));
+    LayoutUnit rootBlockLogicalRight = std::min(inlineDirectionOffset(rootBlock, offsetFromRootBlock) + logicalLeft,
+        std::min(logicalRightSelectionOffset(rootBlock, logicalTop, cache), logicalRightSelectionOffset(rootBlock, logicalTop + logicalHeight, cache)));
+    LayoutUnit rootBlockLogicalWidth = rootBlockLogicalRight - rootBlockLogicalLeft;
+    if (rootBlockLogicalWidth <= 0)
+        return LayoutRect();
 
-    logicalLeftOffset += marginLogicalLeft();
-
-    const FloatingObjectSet& prevSet = prev->m_floatingObjects->set();
-    FloatingObjectSetIterator prevEnd = prevSet.end();
-    for (FloatingObjectSetIterator prevIt = prevSet.begin(); prevIt != prevEnd; ++prevIt) {
-        FloatingObject* r = *prevIt;
-        if (logicalBottomForFloat(r) > logicalTopOffset) {
-            if (!m_floatingObjects || !m_floatingObjects->set().contains(r)) {
-                LayoutSize offset = isHorizontalWritingMode() ? LayoutSize(logicalLeftOffset, logicalTopOffset) : LayoutSize(logicalTopOffset, logicalLeftOffset);
-                FloatingObject* floatingObj = new FloatingObject(r->type(), LayoutRect(r->frameRect().location() - offset, r->frameRect().size()));
-
-                // Applying the child's margin makes no sense in the case where the child was passed in.
-                // since this margin was added already through the modification of the |logicalLeftOffset| variable
-                // above.  |logicalLeftOffset| will equal the margin in this case, so it's already been taken
-                // into account.  Only apply this code if prev is the parent, since otherwise the left margin
-                // will get applied twice.
-                if (prev != parent()) {
-                    if (isHorizontalWritingMode())
-                        floatingObj->setX(floatingObj->x() + prev->marginLeft());
-                    else
-                        floatingObj->setY(floatingObj->y() + prev->marginTop());
-                }
-               
-                floatingObj->setShouldPaint(false); // We are not in the direct inheritance chain for this float. We will never paint it.
-                floatingObj->m_renderer = r->m_renderer;
-                
-                // We create the floating object list lazily.
-                if (!m_floatingObjects)
-                    createFloatingObjects();
-                m_floatingObjects->add(floatingObj);
-            }
-        }
-    }
+    LayoutRect gapRect = rootBlock.logicalRectToPhysicalRect(rootBlockPhysicalPosition, LayoutRect(rootBlockLogicalLeft, rootBlockLogicalTop, rootBlockLogicalWidth, logicalHeight));
+    if (paintInfo)
+        paintInfo->context().fillRect(snapRectToDevicePixels(gapRect, document().deviceScaleFactor()), selObj->selectionBackgroundColor());
+    return gapRect;
 }
 
-bool RenderBlock::avoidsFloats() const
+LayoutRect RenderBlock::logicalRightSelectionGap(RenderBlock& rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
+    RenderBoxModelObject* selObj, LayoutUnit logicalRight, LayoutUnit logicalTop, LayoutUnit logicalHeight, const LogicalSelectionOffsetCaches& cache, const PaintInfo* paintInfo)
 {
-    // Floats can't intrude into our box if we have a non-auto column count or width.
-    return RenderBox::avoidsFloats() || !style()->hasAutoColumnCount() || !style()->hasAutoColumnWidth();
-}
+    LayoutUnit rootBlockLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalTop;
+    LayoutUnit rootBlockLogicalLeft = std::max(inlineDirectionOffset(rootBlock, offsetFromRootBlock) + logicalRight,
+        std::max(logicalLeftSelectionOffset(rootBlock, logicalTop, cache), logicalLeftSelectionOffset(rootBlock, logicalTop + logicalHeight, cache)));
+    LayoutUnit rootBlockLogicalRight = std::min(logicalRightSelectionOffset(rootBlock, logicalTop, cache), logicalRightSelectionOffset(rootBlock, logicalTop + logicalHeight, cache));
+    LayoutUnit rootBlockLogicalWidth = rootBlockLogicalRight - rootBlockLogicalLeft;
+    if (rootBlockLogicalWidth <= 0)
+        return LayoutRect();
 
-bool RenderBlock::containsFloat(RenderBox* renderer) const
-{
-    return m_floatingObjects && m_floatingObjects->set().contains<RenderBox*, FloatingObjectHashTranslator>(renderer);
+    LayoutRect gapRect = rootBlock.logicalRectToPhysicalRect(rootBlockPhysicalPosition, LayoutRect(rootBlockLogicalLeft, rootBlockLogicalTop, rootBlockLogicalWidth, logicalHeight));
+    if (paintInfo)
+        paintInfo->context().fillRect(snapRectToDevicePixels(gapRect, document().deviceScaleFactor()), selObj->selectionBackgroundColor());
+    return gapRect;
 }
 
-void RenderBlock::markAllDescendantsWithFloatsForLayout(RenderBox* floatToRemove, bool inLayout)
+void RenderBlock::getSelectionGapInfo(SelectionState state, bool& leftGap, bool& rightGap)
 {
-    if (!everHadLayout() && !containsFloats())
-        return;
-
-    MarkingBehavior markParents = inLayout ? MarkOnlyThis : MarkContainingBlockChain;
-    setChildNeedsLayout(true, markParents);
- 
-    if (floatToRemove)
-        removeFloatingObject(floatToRemove);
-
-    // Iterate over our children and mark them as needed.
-    if (!childrenInline()) {
-        for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
-            if ((!floatToRemove && child->isFloatingOrOutOfFlowPositioned()) || !child->isRenderBlock())
-                continue;
-            RenderBlock* childBlock = toRenderBlock(child);
-            if ((floatToRemove ? childBlock->containsFloat(floatToRemove) : childBlock->containsFloats()) || childBlock->shrinkToAvoidFloats())
-                childBlock->markAllDescendantsWithFloatsForLayout(floatToRemove, inLayout);
-        }
-    }
+    bool ltr = style().isLeftToRightDirection();
+    leftGap = (state == RenderObject::SelectionInside) ||
+              (state == RenderObject::SelectionEnd && ltr) ||
+              (state == RenderObject::SelectionStart && !ltr);
+    rightGap = (state == RenderObject::SelectionInside) ||
+               (state == RenderObject::SelectionStart && ltr) ||
+               (state == RenderObject::SelectionEnd && !ltr);
 }
 
-void RenderBlock::markSiblingsWithFloatsForLayout(RenderBox* floatToRemove)
+LayoutUnit RenderBlock::logicalLeftSelectionOffset(RenderBlock& rootBlock, LayoutUnit position, const LogicalSelectionOffsetCaches& cache)
 {
-    if (!m_floatingObjects)
-        return;
-
-    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    FloatingObjectSetIterator end = floatingObjectSet.end();
+    LayoutUnit logicalLeft = logicalLeftOffsetForLine(position, DoNotIndentText);
+    if (logicalLeft == logicalLeftOffsetForContent()) {
+        if (&rootBlock != this) // The border can potentially be further extended by our containingBlock().
+            return cache.containingBlockInfo(*this).logicalLeftSelectionOffset(rootBlock, position + logicalTop());
+        return logicalLeft;
+    }
 
-    for (RenderObject* next = nextSibling(); next; next = next->nextSibling()) {
-        if (!next->isRenderBlock() || next->isFloatingOrOutOfFlowPositioned() || toRenderBlock(next)->avoidsFloats())
-            continue;
+    RenderBlock* cb = this;
+    const LogicalSelectionOffsetCaches* currentCache = &cache;
+    while (cb != &rootBlock) {
+        logicalLeft += cb->logicalLeft();
 
-        RenderBlock* nextBlock = toRenderBlock(next);
-        for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-            RenderBox* floatingBox = (*it)->renderer();
-            if (floatToRemove && floatingBox != floatToRemove)
-                continue;
-            if (nextBlock->containsFloat(floatingBox))
-                nextBlock->markAllDescendantsWithFloatsForLayout(floatingBox);
-        }
+        ASSERT(currentCache);
+        auto info = currentCache->containingBlockInfo(*cb);
+        cb = info.block();
+        currentCache = info.cache();
     }
+    return logicalLeft;
 }
 
-LayoutUnit RenderBlock::getClearDelta(RenderBox* child, LayoutUnit logicalTop)
+LayoutUnit RenderBlock::logicalRightSelectionOffset(RenderBlock& rootBlock, LayoutUnit position, const LogicalSelectionOffsetCaches& cache)
 {
-    // There is no need to compute clearance if we have no floats.
-    if (!containsFloats())
-        return 0;
-    
-    // At least one float is present.  We need to perform the clearance computation.
-    bool clearSet = child->style()->clear() != CNONE;
-    LayoutUnit logicalBottom = 0;
-    switch (child->style()->clear()) {
-        case CNONE:
-            break;
-        case CLEFT:
-            logicalBottom = lowestFloatLogicalBottom(FloatingObject::FloatLeft);
-            break;
-        case CRIGHT:
-            logicalBottom = lowestFloatLogicalBottom(FloatingObject::FloatRight);
-            break;
-        case CBOTH:
-            logicalBottom = lowestFloatLogicalBottom();
-            break;
+    LayoutUnit logicalRight = logicalRightOffsetForLine(position, DoNotIndentText);
+    if (logicalRight == logicalRightOffsetForContent()) {
+        if (&rootBlock != this) // The border can potentially be further extended by our containingBlock().
+            return cache.containingBlockInfo(*this).logicalRightSelectionOffset(rootBlock, position + logicalTop());
+        return logicalRight;
     }
 
-    // We also clear floats if we are too big to sit on the same line as a float (and wish to avoid floats by default).
-    LayoutUnit result = clearSet ? max<LayoutUnit>(0, logicalBottom - logicalTop) : LayoutUnit();
-    if (!result && child->avoidsFloats()) {
-        LayoutUnit newLogicalTop = logicalTop;
-        while (true) {
-            LayoutUnit availableLogicalWidthAtNewLogicalTopOffset = availableLogicalWidthForLine(newLogicalTop, false, logicalHeightForChild(child));
-            if (availableLogicalWidthAtNewLogicalTopOffset == availableLogicalWidthForContent(newLogicalTop))
-                return newLogicalTop - logicalTop;
-
-            RenderRegion* region = regionAtBlockOffset(logicalTopForChild(child));
-            LayoutRect borderBox = child->borderBoxRectInRegion(region, DoNotCacheRenderBoxRegionInfo);
-            LayoutUnit childLogicalWidthAtOldLogicalTopOffset = isHorizontalWritingMode() ? borderBox.width() : borderBox.height();
-
-            // FIXME: None of this is right for perpendicular writing-mode children.
-            LayoutUnit childOldLogicalWidth = child->logicalWidth();
-            LayoutUnit childOldMarginLeft = child->marginLeft();
-            LayoutUnit childOldMarginRight = child->marginRight();
-            LayoutUnit childOldLogicalTop = child->logicalTop();
-
-            child->setLogicalTop(newLogicalTop);
-            child->updateLogicalWidth();
-            region = regionAtBlockOffset(logicalTopForChild(child));
-            borderBox = child->borderBoxRectInRegion(region, DoNotCacheRenderBoxRegionInfo);
-            LayoutUnit childLogicalWidthAtNewLogicalTopOffset = isHorizontalWritingMode() ? borderBox.width() : borderBox.height();
-
-            child->setLogicalTop(childOldLogicalTop);
-            child->setLogicalWidth(childOldLogicalWidth);
-            child->setMarginLeft(childOldMarginLeft);
-            child->setMarginRight(childOldMarginRight);
-            
-            if (childLogicalWidthAtNewLogicalTopOffset <= availableLogicalWidthAtNewLogicalTopOffset) {
-                // Even though we may not be moving, if the logical width did shrink because of the presence of new floats, then
-                // we need to force a relayout as though we shifted. This happens because of the dynamic addition of overhanging floats
-                // from previous siblings when negative margins exist on a child (see the addOverhangingFloats call at the end of collapseMargins).
-                if (childLogicalWidthAtOldLogicalTopOffset != childLogicalWidthAtNewLogicalTopOffset)
-                    child->setChildNeedsLayout(true, MarkOnlyThis);
-                return newLogicalTop - logicalTop;
-            }
+    RenderBlock* cb = this;
+    const LogicalSelectionOffsetCaches* currentCache = &cache;
+    while (cb != &rootBlock) {
+        logicalRight += cb->logicalLeft();
 
-            newLogicalTop = nextFloatLogicalBottomBelow(newLogicalTop);
-            ASSERT(newLogicalTop >= logicalTop);
-            if (newLogicalTop < logicalTop)
-                break;
-        }
-        ASSERT_NOT_REACHED();
+        ASSERT(currentCache);
+        auto info = currentCache->containingBlockInfo(*cb);
+        cb = info.block();
+        currentCache = info.cache();
     }
-    return result;
-}
-
-bool RenderBlock::isPointInOverflowControl(HitTestResult& result, const LayoutPoint& locationInContainer, const LayoutPoint& accumulatedOffset)
-{
-    if (!scrollsOverflow())
-        return false;
-
-    return layer()->hitTestOverflowControls(result, roundedIntPoint(locationInContainer - toLayoutSize(accumulatedOffset)));
+    return logicalRight;
 }
 
-Node* RenderBlock::nodeForHitTest() const
+RenderBlock* RenderBlock::blockBeforeWithinSelectionRoot(LayoutSize& offset) const
 {
-    // If we are in the margins of block elements that are part of a
-    // continuation we're actually still inside the enclosing element
-    // that was split. Use the appropriate inner node.
-    return isAnonymousBlockContinuation() ? continuation()->node() : node();
-}
+    if (isSelectionRoot())
+        return nullptr;
 
-bool RenderBlock::nodeAtPoint(const HitTestRequest& request, HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction hitTestAction)
-{
-    LayoutPoint adjustedLocation(accumulatedOffset + location());
-    LayoutSize localOffset = toLayoutSize(adjustedLocation);
+    const RenderElement* object = this;
+    RenderObject* sibling;
+    do {
+        sibling = object->previousSibling();
+        while (sibling && (!is<RenderBlock>(*sibling) || downcast<RenderBlock>(*sibling).isSelectionRoot()))
+            sibling = sibling->previousSibling();
 
-    if (!isRenderView()) {
-        // Check if we need to do anything at all.
-        LayoutRect overflowBox = visualOverflowRect();
-        flipForWritingMode(overflowBox);
-        overflowBox.moveBy(adjustedLocation);
-        if (!locationInContainer.intersects(overflowBox))
-            return false;
-    }
+        offset -= LayoutSize(downcast<RenderBlock>(*object).logicalLeft(), downcast<RenderBlock>(*object).logicalTop());
+        object = object->parent();
+    } while (!sibling && is<RenderBlock>(object) && !downcast<RenderBlock>(*object).isSelectionRoot());
 
-    if ((hitTestAction == HitTestBlockBackground || hitTestAction == HitTestChildBlockBackground) && isPointInOverflowControl(result, locationInContainer.point(), adjustedLocation)) {
-        updateHitTestResult(result, locationInContainer.point() - localOffset);
-        // FIXME: isPointInOverflowControl() doesn't handle rect-based tests yet.
-        if (!result.addNodeToRectBasedTestResult(nodeForHitTest(), request, locationInContainer))
-           return true;
-    }
+    if (!sibling)
+        return nullptr;
 
-    // If we have clipping, then we can't have any spillout.
-    bool useOverflowClip = hasOverflowClip() && !hasSelfPaintingLayer();
-    bool useClip = (hasControlClip() || useOverflowClip);
-    bool checkChildren = !useClip || (hasControlClip() ? locationInContainer.intersects(controlClipRect(adjustedLocation)) : locationInContainer.intersects(overflowClipRect(adjustedLocation, locationInContainer.region(), IncludeOverlayScrollbarSize)));
-    if (checkChildren) {
-        // Hit test descendants first.
-        LayoutSize scrolledOffset(localOffset);
-        if (hasOverflowClip())
-            scrolledOffset -= scrolledContentOffset();
-
-        // Hit test contents if we don't have columns.
-        if (!hasColumns()) {
-            if (hitTestContents(request, result, locationInContainer, toLayoutPoint(scrolledOffset), hitTestAction)) {
-                updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - localOffset));
-                return true;
-            }
-            if (hitTestAction == HitTestFloat && hitTestFloats(request, result, locationInContainer, toLayoutPoint(scrolledOffset)))
-                return true;
-        } else if (hitTestColumns(request, result, locationInContainer, toLayoutPoint(scrolledOffset), hitTestAction)) {
-            updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - localOffset));
-            return true;
-        }
-    }
+    RenderBlock* beforeBlock = downcast<RenderBlock>(sibling);
 
-    // Check if the point is outside radii.
-    if (!isRenderView() && style()->hasBorderRadius()) {
-        LayoutRect borderRect = borderBoxRect();
-        borderRect.moveBy(adjustedLocation);
-        RoundedRect border = style()->getRoundedBorderFor(borderRect, view());
-        if (!locationInContainer.intersects(border))
-            return false;
-    }
+    offset += LayoutSize(beforeBlock->logicalLeft(), beforeBlock->logicalTop());
 
-    // Now hit test our background
-    if (hitTestAction == HitTestBlockBackground || hitTestAction == HitTestChildBlockBackground) {
-        LayoutRect boundsRect(adjustedLocation, size());
-        if (visibleToHitTesting() && locationInContainer.intersects(boundsRect)) {
-            updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - localOffset));
-            if (!result.addNodeToRectBasedTestResult(nodeForHitTest(), request, locationInContainer, boundsRect))
-                return true;
-        }
+    RenderObject* child = beforeBlock->lastChild();
+    while (is<RenderBlock>(child)) {
+        beforeBlock = downcast<RenderBlock>(child);
+        offset += LayoutSize(beforeBlock->logicalLeft(), beforeBlock->logicalTop());
+        child = beforeBlock->lastChild();
     }
-
-    return false;
+    return beforeBlock;
 }
 
-bool RenderBlock::hitTestFloats(const HitTestRequest& request, HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset)
+void RenderBlock::insertIntoTrackedRendererMaps(RenderBox& descendant, TrackedDescendantsMap*& descendantsMap, TrackedContainerMap*& containerMap, bool forceNewEntry)
 {
-    if (!m_floatingObjects)
-        return false;
-
-    LayoutPoint adjustedLocation = accumulatedOffset;
-    if (isRenderView()) {
-        adjustedLocation += toLayoutSize(toRenderView(this)->frameView()->scrollPosition());
+    if (!descendantsMap) {
+        descendantsMap = new TrackedDescendantsMap;
+        containerMap = new TrackedContainerMap;
     }
-
-    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-    FloatingObjectSetIterator begin = floatingObjectSet.begin();
-    for (FloatingObjectSetIterator it = floatingObjectSet.end(); it != begin;) {
-        --it;
-        FloatingObject* floatingObject = *it;
-        if (floatingObject->shouldPaint() && !floatingObject->m_renderer->hasSelfPaintingLayer()) {
-            LayoutUnit xOffset = xPositionForFloatIncludingMargin(floatingObject) - floatingObject->m_renderer->x();
-            LayoutUnit yOffset = yPositionForFloatIncludingMargin(floatingObject) - floatingObject->m_renderer->y();
-            LayoutPoint childPoint = flipFloatForWritingModeForChild(floatingObject, adjustedLocation + LayoutSize(xOffset, yOffset));
-            if (floatingObject->m_renderer->hitTest(request, result, locationInContainer, childPoint)) {
-                updateHitTestResult(result, locationInContainer.point() - toLayoutSize(childPoint));
-                return true;
-            }
-        }
+    
+    TrackedRendererListHashSet* descendantSet = descendantsMap->get(this);
+    if (!descendantSet) {
+        descendantSet = new TrackedRendererListHashSet;
+        descendantsMap->set(this, std::unique_ptr<TrackedRendererListHashSet>(descendantSet));
     }
-
-    return false;
-}
-
-class ColumnRectIterator {
-    WTF_MAKE_NONCOPYABLE(ColumnRectIterator);
-public:
-    ColumnRectIterator(const RenderBlock& block)
-        : m_block(block)
-        , m_colInfo(block.columnInfo())
-        , m_direction(m_block.style()->isFlippedBlocksWritingMode() ? 1 : -1)
-        , m_isHorizontal(block.isHorizontalWritingMode())
-        , m_logicalLeft(block.logicalLeftOffsetForContent())
-    {
-        int colCount = m_colInfo->columnCount();
-        m_colIndex = colCount - 1;
-        
-        m_currLogicalTopOffset = m_block.initialBlockOffsetForPainting();
-        m_currLogicalTopOffset = colCount * m_block.blockDeltaForPaintingNextColumn();
-        
-        update();
+    
+    if (forceNewEntry) {
+        descendantSet->remove(&descendant);
+        containerMap->remove(&descendant);
     }
-
-    void advance()
-    {
-        ASSERT(hasMore());
-        m_colIndex--;
-        update();
+    
+    bool added = descendantSet->add(&descendant).isNewEntry;
+    if (!added) {
+        ASSERT(containerMap->get(&descendant));
+        ASSERT(containerMap->get(&descendant)->contains(this));
+        return;
     }
+    
+    HashSet<RenderBlock*>* containerSet = containerMap->get(&descendant);
+    if (!containerSet) {
+        containerSet = new HashSet<RenderBlock*>;
+        containerMap->set(&descendant, std::unique_ptr<HashSet<RenderBlock*>>(containerSet));
+    }    
+    ASSERT(!containerSet->contains(this));
+    containerSet->add(this);
+}
 
-    LayoutRect columnRect() const { return m_colRect; }
-    bool hasMore() const { return m_colIndex >= 0; }
+void RenderBlock::removeFromTrackedRendererMaps(RenderBox& descendant, TrackedDescendantsMap*& descendantsMap, TrackedContainerMap*& containerMap)
+{
+    if (!descendantsMap)
+        return;
+    
+    std::unique_ptr<HashSet<RenderBlock*>> containerSet = containerMap->take(&descendant);
+    if (!containerSet)
+        return;
+    
+    for (auto it = containerSet->begin(), end = containerSet->end(); it != end; ++it) {
+        RenderBlock* container = *it;
 
-    void adjust(LayoutSize& offset) const
-    {
-        LayoutUnit currLogicalLeftOffset = (m_isHorizontal ? m_colRect.x() : m_colRect.y()) - m_logicalLeft;
-        offset += m_isHorizontal ? LayoutSize(currLogicalLeftOffset, m_currLogicalTopOffset) : LayoutSize(m_currLogicalTopOffset, currLogicalLeftOffset);
-    }
+        // FIXME: Disabling this assert temporarily until we fix the layout
+        // bugs associated with positioned objects not properly cleared from
+        // their ancestor chain before being moved. See webkit bug 93766.
+        // ASSERT(descendant->isDescendantOf(container));
 
-private:
-    void update()
-    {
-        if (m_colIndex < 0)
-            return;
-        m_colRect = m_block.columnRectAt(const_cast<ColumnInfo*>(m_colInfo), m_colIndex);
-        m_block.flipForWritingMode(m_colRect);
-        m_currLogicalTopOffset -= m_block.blockDeltaForPaintingNextColumn();
+        TrackedDescendantsMap::iterator descendantsMapIterator = descendantsMap->find(container);
+        ASSERT(descendantsMapIterator != descendantsMap->end());
+        if (descendantsMapIterator == descendantsMap->end())
+            continue;
+        TrackedRendererListHashSet* descendantSet = descendantsMapIterator->value.get();
+        ASSERT(descendantSet->contains(&descendant));
+        descendantSet->remove(&descendant);
+        if (descendantSet->isEmpty())
+            descendantsMap->remove(descendantsMapIterator);
     }
+}
 
-    const RenderBlock& m_block;
-    const ColumnInfo* const m_colInfo;
-    const int m_direction;
-    const bool m_isHorizontal;
-    const LayoutUnit m_logicalLeft;
-    int m_colIndex;
-    LayoutUnit m_currLogicalTopOffset;
-    LayoutRect m_colRect;
-};
+TrackedRendererListHashSet* RenderBlock::positionedObjects() const
+{
+    if (gPositionedDescendantsMap)
+        return gPositionedDescendantsMap->get(this);
+    return nullptr;
+}
 
-bool RenderBlock::hitTestColumns(const HitTestRequest& request, HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction hitTestAction)
+void RenderBlock::insertPositionedObject(RenderBox& o)
 {
-    // We need to do multiple passes, breaking up our hit testing into strips.
-    if (!hasColumns())
-        return false;
+    ASSERT(!isAnonymousBlock());
 
-    for (ColumnRectIterator it(*this); it.hasMore(); it.advance()) {
-        LayoutRect hitRect = locationInContainer.boundingBox();
-        LayoutRect colRect = it.columnRect();
-        colRect.moveBy(accumulatedOffset);
-        if (locationInContainer.intersects(colRect)) {
-            // The point is inside this column.
-            // Adjust accumulatedOffset to change where we hit test.
-            LayoutSize offset;
-            it.adjust(offset);
-            LayoutPoint finalLocation = accumulatedOffset + offset;
-            if (!result.isRectBasedTest() || colRect.contains(hitRect))
-                return hitTestContents(request, result, locationInContainer, finalLocation, hitTestAction) || (hitTestAction == HitTestFloat && hitTestFloats(request, result, locationInContainer, finalLocation));
-
-            hitTestContents(request, result, locationInContainer, finalLocation, hitTestAction);
-        }
-    }
+    if (o.isRenderFlowThread())
+        return;
+    
+    insertIntoTrackedRendererMaps(o, gPositionedDescendantsMap, gPositionedContainerMap, isRenderView());
+}
 
-    return false;
+void RenderBlock::removePositionedObject(RenderBox& o)
+{
+    removeFromTrackedRendererMaps(o, gPositionedDescendantsMap, gPositionedContainerMap);
 }
 
-void RenderBlock::adjustForColumnRect(LayoutSize& offset, const LayoutPoint& locationInContainer) const
+void RenderBlock::removePositionedObjects(RenderBlock* o, ContainingBlockState containingBlockState)
 {
-    for (ColumnRectIterator it(*this); it.hasMore(); it.advance()) {
-        LayoutRect colRect = it.columnRect();
-        if (colRect.contains(locationInContainer)) {
-            it.adjust(offset);
-            return;
+    TrackedRendererListHashSet* positionedDescendants = positionedObjects();
+    if (!positionedDescendants)
+        return;
+    
+    Vector<RenderBox*, 16> deadObjects;
+
+    for (auto it = positionedDescendants->begin(), end = positionedDescendants->end(); it != end; ++it) {
+        RenderBox* r = *it;
+        if (!o || r->isDescendantOf(o)) {
+            if (containingBlockState == NewContainingBlock)
+                r->setChildNeedsLayout(MarkOnlyThis);
+            
+            // It is parent blocks job to add positioned child to positioned objects list of its containing block
+            // Parent layout needs to be invalidated to ensure this happens.
+            RenderElement* p = r->parent();
+            while (p && !p->isRenderBlock())
+                p = p->parent();
+            if (p)
+                p->setChildNeedsLayout();
+            
+            deadObjects.append(r);
         }
     }
+    
+    for (unsigned i = 0; i < deadObjects.size(); i++)
+        removePositionedObject(*deadObjects.at(i));
 }
 
-bool RenderBlock::hitTestContents(const HitTestRequest& request, HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction hitTestAction)
+void RenderBlock::addPercentHeightDescendant(RenderBox& descendant)
 {
-    if (childrenInline() && !isTable()) {
-        // We have to hit-test our line boxes.
-        if (m_lineBoxes.hitTest(this, request, result, locationInContainer, accumulatedOffset, hitTestAction))
-            return true;
-    } else {
-        // Hit test our children.
-        HitTestAction childHitTest = hitTestAction;
-        if (hitTestAction == HitTestChildBlockBackgrounds)
-            childHitTest = HitTestChildBlockBackground;
-        for (RenderBox* child = lastChildBox(); child; child = child->previousSiblingBox()) {
-            LayoutPoint childPoint = flipForWritingModeForChild(child, accumulatedOffset);
-            if (!child->hasSelfPaintingLayer() && !child->isFloating() && child->nodeAtPoint(request, result, locationInContainer, childPoint, childHitTest))
-                return true;
-        }
-    }
-
-    return false;
+    insertIntoTrackedRendererMaps(descendant, gPercentHeightDescendantsMap, gPercentHeightContainerMap);
 }
 
-Position RenderBlock::positionForBox(InlineBox *box, bool start) const
+void RenderBlock::removePercentHeightDescendant(RenderBox& descendant)
 {
-    if (!box)
-        return Position();
-
-    if (!box->renderer()->nonPseudoNode())
-        return createLegacyEditingPosition(nonPseudoNode(), start ? caretMinOffset() : caretMaxOffset());
-
-    if (!box->isInlineTextBox())
-        return createLegacyEditingPosition(box->renderer()->nonPseudoNode(), start ? box->renderer()->caretMinOffset() : box->renderer()->caretMaxOffset());
-
-    InlineTextBox* textBox = toInlineTextBox(box);
-    return createLegacyEditingPosition(box->renderer()->nonPseudoNode(), start ? textBox->start() : textBox->start() + textBox->len());
+    removeFromTrackedRendererMaps(descendant, gPercentHeightDescendantsMap, gPercentHeightContainerMap);
 }
 
-static inline bool isEditingBoundary(RenderObject* ancestor, RenderObject* child)
+TrackedRendererListHashSet* RenderBlock::percentHeightDescendants() const
 {
-    ASSERT(!ancestor || ancestor->nonPseudoNode());
-    ASSERT(child && child->nonPseudoNode());
-    return !ancestor || !ancestor->parent() || (ancestor->hasLayer() && ancestor->parent()->isRenderView())
-        || ancestor->nonPseudoNode()->rendererIsEditable() == child->nonPseudoNode()->rendererIsEditable();
+    return gPercentHeightDescendantsMap ? gPercentHeightDescendantsMap->get(this) : 0;
 }
 
-// FIXME: This function should go on RenderObject as an instance method. Then
-// all cases in which positionForPoint recurs could call this instead to
-// prevent crossing editable boundaries. This would require many tests.
-static VisiblePosition positionForPointRespectingEditingBoundaries(RenderBlock* parent, RenderBox* child, const LayoutPoint& pointInParentCoordinates)
+bool RenderBlock::hasPercentHeightContainerMap()
 {
-    LayoutPoint childLocation = child->location();
-    if (child->isInFlowPositioned())
-        childLocation += child->offsetForInFlowPosition();
-
-    // FIXME: This is wrong if the child's writing-mode is different from the parent's.
-    LayoutPoint pointInChildCoordinates(toLayoutPoint(pointInParentCoordinates - childLocation));
-
-    // If this is an anonymous renderer, we just recur normally
-    Node* childNode = child->nonPseudoNode();
-    if (!childNode)
-        return child->positionForPoint(pointInChildCoordinates);
-
-    // Otherwise, first make sure that the editability of the parent and child agree.
-    // If they don't agree, then we return a visible position just before or after the child
-    RenderObject* ancestor = parent;
-    while (ancestor && !ancestor->nonPseudoNode())
-        ancestor = ancestor->parent();
-
-    // If we can't find an ancestor to check editability on, or editability is unchanged, we recur like normal
-    if (isEditingBoundary(ancestor, child))
-        return child->positionForPoint(pointInChildCoordinates);
+    return gPercentHeightContainerMap;
+}
 
-    // Otherwise return before or after the child, depending on if the click was to the logical left or logical right of the child
-    LayoutUnit childMiddle = parent->logicalWidthForChild(child) / 2;
-    LayoutUnit logicalLeft = parent->isHorizontalWritingMode() ? pointInChildCoordinates.x() : pointInChildCoordinates.y();
-    if (logicalLeft < childMiddle)
-        return ancestor->createVisiblePosition(childNode->nodeIndex(), DOWNSTREAM);
-    return ancestor->createVisiblePosition(childNode->nodeIndex() + 1, UPSTREAM);
+bool RenderBlock::hasPercentHeightDescendant(RenderBox& descendant)
+{
+    // We don't null check gPercentHeightContainerMap since the caller
+    // already ensures this and we need to call this function on every
+    // descendant in clearPercentHeightDescendantsFrom().
+    ASSERT(gPercentHeightContainerMap);
+    return gPercentHeightContainerMap->contains(&descendant);
 }
 
-VisiblePosition RenderBlock::positionForPointWithInlineChildren(const LayoutPoint& pointInLogicalContents)
+void RenderBlock::removePercentHeightDescendantIfNeeded(RenderBox& descendant)
 {
-    ASSERT(childrenInline());
+    // We query the map directly, rather than looking at style's
+    // logicalHeight()/logicalMinHeight()/logicalMaxHeight() since those
+    // can change with writing mode/directional changes.
+    if (!hasPercentHeightContainerMap())
+        return;
 
-    if (!firstRootBox())
-        return createVisiblePosition(0, DOWNSTREAM);
+    if (!hasPercentHeightDescendant(descendant))
+        return;
 
-    bool linesAreFlipped = style()->isFlippedLinesWritingMode();
-    bool blocksAreFlipped = style()->isFlippedBlocksWritingMode();
+    removePercentHeightDescendant(descendant);
+}
 
-    // look for the closest line box in the root box which is at the passed-in y coordinate
-    InlineBox* closestBox = 0;
-    RootInlineBox* firstRootBoxWithChildren = 0;
-    RootInlineBox* lastRootBoxWithChildren = 0;
-    for (RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox()) {
-        if (!root->firstLeafChild())
+void RenderBlock::clearPercentHeightDescendantsFrom(RenderBox& parent)
+{
+    ASSERT(gPercentHeightContainerMap);
+    for (RenderObject* child = parent.firstChild(); child; child = child->nextInPreOrder(&parent)) {
+        if (!is<RenderBox>(*child))
+            continue;
+ 
+        auto& box = downcast<RenderBox>(*child);
+        if (!hasPercentHeightDescendant(box))
             continue;
-        if (!firstRootBoxWithChildren)
-            firstRootBoxWithChildren = root;
-
-        if (!linesAreFlipped && root->isFirstAfterPageBreak() && (pointInLogicalContents.y() < root->lineTopWithLeading()
-            || (blocksAreFlipped && pointInLogicalContents.y() == root->lineTopWithLeading())))
-            break;
-
-        lastRootBoxWithChildren = root;
-
-        // check if this root line box is located at this y coordinate
-        if (pointInLogicalContents.y() < root->selectionBottom() || (blocksAreFlipped && pointInLogicalContents.y() == root->selectionBottom())) {
-            if (linesAreFlipped) {
-                RootInlineBox* nextRootBoxWithChildren = root->nextRootBox();
-                while (nextRootBoxWithChildren && !nextRootBoxWithChildren->firstLeafChild())
-                    nextRootBoxWithChildren = nextRootBoxWithChildren->nextRootBox();
-
-                if (nextRootBoxWithChildren && nextRootBoxWithChildren->isFirstAfterPageBreak() && (pointInLogicalContents.y() > nextRootBoxWithChildren->lineTopWithLeading()
-                    || (!blocksAreFlipped && pointInLogicalContents.y() == nextRootBoxWithChildren->lineTopWithLeading())))
-                    continue;
-            }
-            closestBox = root->closestLeafChildForLogicalLeftPosition(pointInLogicalContents.x());
-            if (closestBox)
-                break;
-        }
-    }
-
-    bool moveCaretToBoundary = document()->frame()->editor().behavior().shouldMoveCaretToHorizontalBoundaryWhenPastTopOrBottom();
-
-    if (!moveCaretToBoundary && !closestBox && lastRootBoxWithChildren) {
-        // y coordinate is below last root line box, pretend we hit it
-        closestBox = lastRootBoxWithChildren->closestLeafChildForLogicalLeftPosition(pointInLogicalContents.x());
-    }
-
-    if (closestBox) {
-        if (moveCaretToBoundary) {
-            LayoutUnit firstRootBoxWithChildrenTop = min<LayoutUnit>(firstRootBoxWithChildren->selectionTop(), firstRootBoxWithChildren->logicalTop());
-            if (pointInLogicalContents.y() < firstRootBoxWithChildrenTop
-                || (blocksAreFlipped && pointInLogicalContents.y() == firstRootBoxWithChildrenTop)) {
-                InlineBox* box = firstRootBoxWithChildren->firstLeafChild();
-                if (box->isLineBreak()) {
-                    if (InlineBox* newBox = box->nextLeafChildIgnoringLineBreak())
-                        box = newBox;
-                }
-                // y coordinate is above first root line box, so return the start of the first
-                return VisiblePosition(positionForBox(box, true), DOWNSTREAM);
-            }
-        }
 
-        // pass the box a top position that is inside it
-        LayoutPoint point(pointInLogicalContents.x(), closestBox->root()->blockDirectionPointInLine());
-        if (!isHorizontalWritingMode())
-            point = point.transposedPoint();
-        if (closestBox->renderer()->isReplaced())
-            return positionForPointRespectingEditingBoundaries(this, toRenderBox(closestBox->renderer()), point);
-        return closestBox->renderer()->positionForPoint(point);
+        removePercentHeightDescendant(box);
     }
+}
 
-    if (lastRootBoxWithChildren) {
-        // We hit this case for Mac behavior when the Y coordinate is below the last box.
-        ASSERT(moveCaretToBoundary);
-        InlineBox* logicallyLastBox;
-        if (lastRootBoxWithChildren->getLogicalEndBoxWithNode(logicallyLastBox))
-            return VisiblePosition(positionForBox(logicallyLastBox, false), DOWNSTREAM);
-    }
+LayoutUnit RenderBlock::textIndentOffset() const
+{
+    LayoutUnit cw = 0;
+    if (style().textIndent().isPercentOrCalculated())
+        cw = containingBlock()->availableLogicalWidth();
+    return minimumValueForLength(style().textIndent(), cw);
+}
 
-    // Can't reach this. We have a root line box, but it has no kids.
-    // FIXME: This should ASSERT_NOT_REACHED(), but clicking on placeholder text
-    // seems to hit this code path.
-    return createVisiblePosition(0, DOWNSTREAM);
+LayoutUnit RenderBlock::logicalLeftOffsetForContent(RenderRegion* region) const
+{
+    LayoutUnit logicalLeftOffset = style().isHorizontalWritingMode() ? borderLeft() + paddingLeft() : borderTop() + paddingTop();
+    if (!region)
+        return logicalLeftOffset;
+    LayoutRect boxRect = borderBoxRectInRegion(region);
+    return logicalLeftOffset + (isHorizontalWritingMode() ? boxRect.x() : boxRect.y());
 }
 
-static inline bool isChildHitTestCandidate(RenderBox* box)
+LayoutUnit RenderBlock::logicalRightOffsetForContent(RenderRegion* region) const
 {
-    return box->height() && box->style()->visibility() == VISIBLE && !box->isFloatingOrOutOfFlowPositioned();
+    LayoutUnit logicalRightOffset = style().isHorizontalWritingMode() ? borderLeft() + paddingLeft() : borderTop() + paddingTop();
+    logicalRightOffset += availableLogicalWidth();
+    if (!region)
+        return logicalRightOffset;
+    LayoutRect boxRect = borderBoxRectInRegion(region);
+    return logicalRightOffset - (logicalWidth() - (isHorizontalWritingMode() ? boxRect.maxX() : boxRect.maxY()));
 }
 
-VisiblePosition RenderBlock::positionForPoint(const LayoutPoint& point)
+LayoutUnit RenderBlock::adjustLogicalLeftOffsetForLine(LayoutUnit offsetFromFloats, bool applyTextIndent) const
 {
-    if (isTable())
-        return RenderBox::positionForPoint(point);
+    LayoutUnit left = offsetFromFloats;
 
-    if (isReplaced()) {
-        // FIXME: This seems wrong when the object's writing-mode doesn't match the line's writing-mode.
-        LayoutUnit pointLogicalLeft = isHorizontalWritingMode() ? point.x() : point.y();
-        LayoutUnit pointLogicalTop = isHorizontalWritingMode() ? point.y() : point.x();
+    if (applyTextIndent && style().isLeftToRightDirection())
+        left += textIndentOffset();
 
-        if (pointLogicalTop < 0 || (pointLogicalTop < logicalHeight() && pointLogicalLeft < 0))
-            return createVisiblePosition(caretMinOffset(), DOWNSTREAM);
-        if (pointLogicalTop >= logicalHeight() || (pointLogicalTop >= 0 && pointLogicalLeft >= logicalWidth()))
-            return createVisiblePosition(caretMaxOffset(), DOWNSTREAM);
-    } 
+    if (style().lineAlign() == LineAlignNone)
+        return left;
+    
+    // Push in our left offset so that it is aligned with the character grid.
+    LayoutState* layoutState = view().layoutState();
+    if (!layoutState)
+        return left;
 
-    LayoutPoint pointInContents = point;
-    offsetForContents(pointInContents);
-    LayoutPoint pointInLogicalContents(pointInContents);
-    if (!isHorizontalWritingMode())
-        pointInLogicalContents = pointInLogicalContents.transposedPoint();
+    RenderBlock* lineGrid = layoutState->lineGrid();
+    if (!lineGrid || lineGrid->style().writingMode() != style().writingMode())
+        return left;
 
-    if (childrenInline())
-        return positionForPointWithInlineChildren(pointInLogicalContents);
+    // FIXME: Should letter-spacing apply? This is complicated since it doesn't apply at the edge?
+    float maxCharWidth = lineGrid->style().fontCascade().primaryFont().maxCharWidth();
+    if (!maxCharWidth)
+        return left;
 
-    RenderBox* lastCandidateBox = lastChildBox();
-    while (lastCandidateBox && !isChildHitTestCandidate(lastCandidateBox))
-        lastCandidateBox = lastCandidateBox->previousSiblingBox();
+    LayoutUnit lineGridOffset = lineGrid->isHorizontalWritingMode() ? layoutState->lineGridOffset().width(): layoutState->lineGridOffset().height();
+    LayoutUnit layoutOffset = lineGrid->isHorizontalWritingMode() ? layoutState->layoutOffset().width() : layoutState->layoutOffset().height();
+    
+    // Push in to the nearest character width (truncated so that we pixel snap left).
+    // FIXME: Should be patched when subpixel layout lands, since this calculation doesn't have to pixel snap
+    // any more (https://bugs.webkit.org/show_bug.cgi?id=79946).
+    // FIXME: This is wrong for RTL (https://bugs.webkit.org/show_bug.cgi?id=79945).
+    // FIXME: This doesn't work with columns or regions (https://bugs.webkit.org/show_bug.cgi?id=79942).
+    // FIXME: This doesn't work when the inline position of the object isn't set ahead of time.
+    // FIXME: Dynamic changes to the font or to the inline position need to result in a deep relayout.
+    // (https://bugs.webkit.org/show_bug.cgi?id=79944)
+    float remainder = fmodf(maxCharWidth - fmodf(left + layoutOffset - lineGridOffset, maxCharWidth), maxCharWidth);
+    left += remainder;
+    return left;
+}
 
-    bool blocksAreFlipped = style()->isFlippedBlocksWritingMode();
-    if (lastCandidateBox) {
-        if (pointInLogicalContents.y() > logicalTopForChild(lastCandidateBox)
-            || (!blocksAreFlipped && pointInLogicalContents.y() == logicalTopForChild(lastCandidateBox)))
-            return positionForPointRespectingEditingBoundaries(this, lastCandidateBox, pointInContents);
+LayoutUnit RenderBlock::adjustLogicalRightOffsetForLine(LayoutUnit offsetFromFloats, bool applyTextIndent) const
+{
+    LayoutUnit right = offsetFromFloats;
+    
+    if (applyTextIndent && !style().isLeftToRightDirection())
+        right -= textIndentOffset();
+    
+    if (style().lineAlign() == LineAlignNone)
+        return right;
+    
+    // Push in our right offset so that it is aligned with the character grid.
+    LayoutState* layoutState = view().layoutState();
+    if (!layoutState)
+        return right;
 
-        for (RenderBox* childBox = firstChildBox(); childBox; childBox = childBox->nextSiblingBox()) {
-            if (!isChildHitTestCandidate(childBox))
-                continue;
-            LayoutUnit childLogicalBottom = logicalTopForChild(childBox) + logicalHeightForChild(childBox);
-            // We hit child if our click is above the bottom of its padding box (like IE6/7 and FF3).
-            if (isChildHitTestCandidate(childBox) && (pointInLogicalContents.y() < childLogicalBottom
-                || (blocksAreFlipped && pointInLogicalContents.y() == childLogicalBottom)))
-                return positionForPointRespectingEditingBoundaries(this, childBox, pointInContents);
-        }
-    }
+    RenderBlock* lineGrid = layoutState->lineGrid();
+    if (!lineGrid || lineGrid->style().writingMode() != style().writingMode())
+        return right;
 
-    // We only get here if there are no hit test candidate children below the click.
-    return RenderBox::positionForPoint(point);
+    // FIXME: Should letter-spacing apply? This is complicated since it doesn't apply at the edge?
+    float maxCharWidth = lineGrid->style().fontCascade().primaryFont().maxCharWidth();
+    if (!maxCharWidth)
+        return right;
+
+    LayoutUnit lineGridOffset = lineGrid->isHorizontalWritingMode() ? layoutState->lineGridOffset().width(): layoutState->lineGridOffset().height();
+    LayoutUnit layoutOffset = lineGrid->isHorizontalWritingMode() ? layoutState->layoutOffset().width() : layoutState->layoutOffset().height();
+    
+    // Push in to the nearest character width (truncated so that we pixel snap right).
+    // FIXME: Should be patched when subpixel layout lands, since this calculation doesn't have to pixel snap
+    // any more (https://bugs.webkit.org/show_bug.cgi?id=79946).
+    // FIXME: This is wrong for RTL (https://bugs.webkit.org/show_bug.cgi?id=79945).
+    // FIXME: This doesn't work with columns or regions (https://bugs.webkit.org/show_bug.cgi?id=79942).
+    // FIXME: This doesn't work when the inline position of the object isn't set ahead of time.
+    // FIXME: Dynamic changes to the font or to the inline position need to result in a deep relayout.
+    // (https://bugs.webkit.org/show_bug.cgi?id=79944)
+    float remainder = fmodf(fmodf(right + layoutOffset - lineGridOffset, maxCharWidth), maxCharWidth);
+    right -= ceilf(remainder);
+    return right;
 }
 
-void RenderBlock::offsetForContents(LayoutPoint& offset) const
+bool RenderBlock::avoidsFloats() const
 {
-    offset = flipForWritingMode(offset);
-
-    if (hasOverflowClip())
-        offset += scrolledContentOffset();
+    // Floats can't intrude into our box if we have a non-auto column count or width.
+    return RenderBox::avoidsFloats() || style().hasFlowFrom();
+}
 
-    if (hasColumns())
-        adjustPointToColumnContents(offset);
+bool RenderBlock::isPointInOverflowControl(HitTestResult& result, const LayoutPoint& locationInContainer, const LayoutPoint& accumulatedOffset)
+{
+    if (!scrollsOverflow())
+        return false;
 
-    offset = flipForWritingMode(offset);
+    return layer()->hitTestOverflowControls(result, roundedIntPoint(locationInContainer - toLayoutSize(accumulatedOffset)));
 }
 
-LayoutUnit RenderBlock::availableLogicalWidth() const
+Node* RenderBlock::nodeForHitTest() const
 {
-    // If we have multiple columns, then the available logical width is reduced to our column width.
-    if (hasColumns())
-        return desiredColumnWidth();
-    return RenderBox::availableLogicalWidth();
+    // If we are in the margins of block elements that are part of a
+    // continuation we're actually still inside the enclosing element
+    // that was split. Use the appropriate inner node.
+    if (isRenderView())
+        return &document();
+    return isAnonymousBlockContinuation() ? continuation()->element() : element();
 }
 
-int RenderBlock::columnGap() const
+bool RenderBlock::nodeAtPoint(const HitTestRequest& request, HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction hitTestAction)
 {
-    if (style()->hasNormalColumnGap())
-        return style()->fontDescription().computedPixelSize(); // "1em" is recommended as the normal gap setting. Matches <p> margins.
-    return static_cast<int>(style()->columnGap());
-}
+    LayoutPoint adjustedLocation(accumulatedOffset + location());
+    LayoutSize localOffset = toLayoutSize(adjustedLocation);
 
-void RenderBlock::calcColumnWidth()
-{   
-    if (document()->regionBasedColumnsEnabled())
-        return;
+    RenderFlowThread* flowThread = flowThreadContainingBlock();
+    RenderNamedFlowFragment* namedFlowFragment = flowThread ? downcast<RenderNamedFlowFragment>(flowThread->currentRegion()) : nullptr;
+    // If we are now searching inside a region, make sure this element
+    // is being fragmented into this region.
+    if (namedFlowFragment && !flowThread->objectShouldFragmentInFlowRegion(this, namedFlowFragment))
+        return false;
 
-    // Calculate our column width and column count.
-    // FIXME: Can overflow on fast/block/float/float-not-removed-from-next-sibling4.html, see https://bugs.webkit.org/show_bug.cgi?id=68744
-    unsigned desiredColumnCount = 1;
-    LayoutUnit desiredColumnWidth = contentLogicalWidth();
-    
-    // For now, we don't support multi-column layouts when printing, since we have to do a lot of work for proper pagination.
-    if (document()->paginated() || (style()->hasAutoColumnCount() && style()->hasAutoColumnWidth()) || !style()->hasInlineColumnAxis()) {
-        setDesiredColumnCountAndWidth(desiredColumnCount, desiredColumnWidth);
-        return;
-    }
-        
-    LayoutUnit availWidth = desiredColumnWidth;
-    LayoutUnit colGap = columnGap();
-    LayoutUnit colWidth = max<LayoutUnit>(1, LayoutUnit(style()->columnWidth()));
-    int colCount = max<int>(1, style()->columnCount());
-
-    if (style()->hasAutoColumnWidth() && !style()->hasAutoColumnCount()) {
-        desiredColumnCount = colCount;
-        desiredColumnWidth = max<LayoutUnit>(0, (availWidth - ((desiredColumnCount - 1) * colGap)) / desiredColumnCount);
-    } else if (!style()->hasAutoColumnWidth() && style()->hasAutoColumnCount()) {
-        desiredColumnCount = max<LayoutUnit>(1, (availWidth + colGap) / (colWidth + colGap));
-        desiredColumnWidth = ((availWidth + colGap) / desiredColumnCount) - colGap;
-    } else {
-        desiredColumnCount = max<LayoutUnit>(min<LayoutUnit>(colCount, (availWidth + colGap) / (colWidth + colGap)), 1);
-        desiredColumnWidth = ((availWidth + colGap) / desiredColumnCount) - colGap;
+    if (!isRenderView()) {
+        // Check if we need to do anything at all.
+        LayoutRect overflowBox = visualOverflowRect();
+        flipForWritingMode(overflowBox);
+        overflowBox.moveBy(adjustedLocation);
+        if (!locationInContainer.intersects(overflowBox))
+            return false;
     }
-    setDesiredColumnCountAndWidth(desiredColumnCount, desiredColumnWidth);
-}
 
-bool RenderBlock::requiresColumns(int desiredColumnCount) const
-{
-    // If overflow-y is set to paged-x or paged-y on the body or html element, we'll handle the paginating
-    // in the RenderView instead.
-    bool isPaginated = (style()->overflowY() == OPAGEDX || style()->overflowY() == OPAGEDY) && !(isRoot() || isBody());
+    if ((hitTestAction == HitTestBlockBackground || hitTestAction == HitTestChildBlockBackground) && isPointInOverflowControl(result, locationInContainer.point(), adjustedLocation)) {
+        updateHitTestResult(result, locationInContainer.point() - localOffset);
+        // FIXME: isPointInOverflowControl() doesn't handle rect-based tests yet.
+        if (!result.addNodeToRectBasedTestResult(nodeForHitTest(), request, locationInContainer))
+           return true;
+    }
 
-    return firstChild()
-        && (desiredColumnCount != 1 || !style()->hasAutoColumnWidth() || !style()->hasInlineColumnAxis() || isPaginated)
-        && !firstChild()->isAnonymousColumnsBlock()
-        && !firstChild()->isAnonymousColumnSpanBlock();
-}
+    if (style().clipPath()) {
+        switch (style().clipPath()->type()) {
+        case ClipPathOperation::Shape: {
+            auto& clipPath = downcast<ShapeClipPathOperation>(*style().clipPath());
 
-void RenderBlock::setDesiredColumnCountAndWidth(int count, LayoutUnit width)
-{
-    bool destroyColumns = !requiresColumns(count);
-    if (destroyColumns) {
-        if (hasColumns()) {
-            gColumnInfoMap->take(this);
-            setHasColumns(false);
+            LayoutRect referenceBoxRect;
+            switch (clipPath.referenceBox()) {
+            case CSSBoxType::MarginBox:
+                referenceBoxRect = marginBoxRect();
+                break;
+            case CSSBoxType::BorderBox:
+                referenceBoxRect = borderBoxRect();
+                break;
+            case CSSBoxType::PaddingBox:
+                referenceBoxRect = paddingBoxRect();
+                break;
+            case CSSBoxType::ContentBox:
+                referenceBoxRect = contentBoxRect();
+                break;
+            case CSSBoxType::BoxMissing:
+            case CSSBoxType::Fill:
+            case CSSBoxType::Stroke:
+            case CSSBoxType::ViewBox:
+                referenceBoxRect = borderBoxRect();
+            }
+            if (!clipPath.pathForReferenceRect(referenceBoxRect).contains(locationInContainer.point() - localOffset, clipPath.windRule()))
+                return false;
+            break;
+        }
+        case ClipPathOperation::Reference: {
+            const auto& referenceClipPathOperation = downcast<ReferenceClipPathOperation>(*style().clipPath());
+            auto* element = document().getElementById(referenceClipPathOperation.fragment());
+            if (!element || !element->renderer())
+                break;
+            if (!is<SVGClipPathElement>(*element))
+                break;
+            auto& clipper = downcast<RenderSVGResourceClipper>(*element->renderer());
+            if (!clipper.hitTestClipContent(FloatRect(borderBoxRect()), FloatPoint(locationInContainer.point() - localOffset)))
+                return false;
+            break;
         }
-    } else {
-        ColumnInfo* info;
-        if (hasColumns())
-            info = gColumnInfoMap->get(this);
-        else {
-            if (!gColumnInfoMap)
-                gColumnInfoMap = new ColumnInfoMap;
-            info = new ColumnInfo;
-            gColumnInfoMap->add(this, adoptPtr(info));
-            setHasColumns(true);
+        case ClipPathOperation::Box:
+            break;
         }
-        info->setDesiredColumnCount(count);
-        info->setDesiredColumnWidth(width);
-        info->setProgressionAxis(style()->hasInlineColumnAxis() ? ColumnInfo::InlineAxis : ColumnInfo::BlockAxis);
-        info->setProgressionIsReversed(style()->columnProgression() == ReverseColumnProgression);
     }
-}
 
-void RenderBlock::updateColumnInfoFromStyle(RenderStyle* style)
-{
-    if (!hasColumns())
-        return;
+    // If we have clipping, then we can't have any spillout.
+    bool useOverflowClip = hasOverflowClip() && !hasSelfPaintingLayer();
+    bool useClip = (hasControlClip() || useOverflowClip);
+    bool checkChildren = !useClip || (hasControlClip() ? locationInContainer.intersects(controlClipRect(adjustedLocation)) : locationInContainer.intersects(overflowClipRect(adjustedLocation, namedFlowFragment, IncludeOverlayScrollbarSize)));
+    if (checkChildren) {
+        // Hit test descendants first.
+        LayoutSize scrolledOffset(localOffset - scrolledContentOffset());
 
-    ColumnInfo* info = gColumnInfoMap->get(this);
+        if (hitTestAction == HitTestFloat && hitTestFloats(request, result, locationInContainer, toLayoutPoint(scrolledOffset)))
+            return true;
+        if (hitTestContents(request, result, locationInContainer, toLayoutPoint(scrolledOffset), hitTestAction)) {
+            updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - localOffset));
+            return true;
+        }
+    }
 
-    bool needsLayout = false;
-    ColumnInfo::Axis oldAxis = info->progressionAxis();
-    ColumnInfo::Axis newAxis = style->hasInlineColumnAxis() ? ColumnInfo::InlineAxis : ColumnInfo::BlockAxis;
-    if (oldAxis != newAxis) {
-        info->setProgressionAxis(newAxis);
-        needsLayout = true;
+    // Check if the point is outside radii.
+    if (!isRenderView() && style().hasBorderRadius()) {
+        LayoutRect borderRect = borderBoxRect();
+        borderRect.moveBy(adjustedLocation);
+        RoundedRect border = style().getRoundedBorderFor(borderRect);
+        if (!locationInContainer.intersects(border))
+            return false;
     }
 
-    bool oldProgressionIsReversed = info->progressionIsReversed();
-    bool newProgressionIsReversed = style->columnProgression() == ReverseColumnProgression;
-    if (oldProgressionIsReversed != newProgressionIsReversed) {
-        info->setProgressionIsReversed(newProgressionIsReversed);
-        needsLayout = true;
+    // Now hit test our background
+    if (hitTestAction == HitTestBlockBackground || hitTestAction == HitTestChildBlockBackground) {
+        LayoutRect boundsRect(adjustedLocation, size());
+        if (visibleToHitTesting() && locationInContainer.intersects(boundsRect)) {
+            updateHitTestResult(result, flipForWritingMode(locationInContainer.point() - localOffset));
+            if (!result.addNodeToRectBasedTestResult(nodeForHitTest(), request, locationInContainer, boundsRect))
+                return true;
+        }
     }
 
-    if (needsLayout)
-        setNeedsLayoutAndPrefWidthsRecalc();
+    return false;
 }
 
-LayoutUnit RenderBlock::desiredColumnWidth() const
+bool RenderBlock::hitTestContents(const HitTestRequest& request, HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction hitTestAction)
 {
-    if (!hasColumns())
-        return contentLogicalWidth();
-    return gColumnInfoMap->get(this)->desiredColumnWidth();
-}
+    if (childrenInline() && !isTable())
+        return hitTestInlineChildren(request, result, locationInContainer, accumulatedOffset, hitTestAction);
 
-unsigned RenderBlock::desiredColumnCount() const
-{
-    if (!hasColumns())
-        return 1;
-    return gColumnInfoMap->get(this)->desiredColumnCount();
-}
+    // Hit test our children.
+    HitTestAction childHitTest = hitTestAction;
+    if (hitTestAction == HitTestChildBlockBackgrounds)
+        childHitTest = HitTestChildBlockBackground;
+    for (auto* child = lastChildBox(); child; child = child->previousSiblingBox()) {
+        LayoutPoint childPoint = flipForWritingModeForChild(child, accumulatedOffset);
+        if (!child->hasSelfPaintingLayer() && !child->isFloating() && child->nodeAtPoint(request, result, locationInContainer, childPoint, childHitTest))
+            return true;
+    }
 
-ColumnInfo* RenderBlock::columnInfo() const
-{
-    if (!hasColumns())
-        return 0;
-    return gColumnInfoMap->get(this);    
+    return false;
 }
 
-unsigned RenderBlock::columnCount(ColumnInfo* colInfo) const
+static inline bool isEditingBoundary(RenderElement* ancestor, RenderObject& child)
 {
-    ASSERT(hasColumns());
-    ASSERT(gColumnInfoMap->get(this) == colInfo);
-    return colInfo->columnCount();
+    ASSERT(!ancestor || ancestor->nonPseudoElement());
+    ASSERT(child.nonPseudoNode());
+    return !ancestor || !ancestor->parent() || (ancestor->hasLayer() && ancestor->parent()->isRenderView())
+        || ancestor->nonPseudoElement()->hasEditableStyle() == child.nonPseudoNode()->hasEditableStyle();
 }
 
-LayoutRect RenderBlock::columnRectAt(ColumnInfo* colInfo, unsigned index) const
+// FIXME: This function should go on RenderObject as an instance method. Then
+// all cases in which positionForPoint recurs could call this instead to
+// prevent crossing editable boundaries. This would require many tests.
+VisiblePosition positionForPointRespectingEditingBoundaries(RenderBlock& parent, RenderBox& child, const LayoutPoint& pointInParentCoordinates)
 {
-    ASSERT(hasColumns() && gColumnInfoMap->get(this) == colInfo);
-
-    // Compute the appropriate rect based off our information.
-    LayoutUnit colLogicalWidth = colInfo->desiredColumnWidth();
-    LayoutUnit colLogicalHeight = colInfo->columnHeight();
-    LayoutUnit colLogicalTop = borderAndPaddingBefore();
-    LayoutUnit colLogicalLeft = logicalLeftOffsetForContent();
-    LayoutUnit colGap = columnGap();
-    if (colInfo->progressionAxis() == ColumnInfo::InlineAxis) {
-        if (style()->isLeftToRightDirection() ^ colInfo->progressionIsReversed())
-            colLogicalLeft += index * (colLogicalWidth + colGap);
-        else
-            colLogicalLeft += contentLogicalWidth() - colLogicalWidth - index * (colLogicalWidth + colGap);
-    } else {
-        if (!colInfo->progressionIsReversed())
-            colLogicalTop += index * (colLogicalHeight + colGap);
-        else
-            colLogicalTop += contentLogicalHeight() - colLogicalHeight - index * (colLogicalHeight + colGap);
-    }
+    LayoutPoint childLocation = child.location();
+    if (child.isInFlowPositioned())
+        childLocation += child.offsetForInFlowPosition();
 
-    if (isHorizontalWritingMode())
-        return LayoutRect(colLogicalLeft, colLogicalTop, colLogicalWidth, colLogicalHeight);
-    return LayoutRect(colLogicalTop, colLogicalLeft, colLogicalHeight, colLogicalWidth);
-}
+    // FIXME: This is wrong if the child's writing-mode is different from the parent's.
+    LayoutPoint pointInChildCoordinates(toLayoutPoint(pointInParentCoordinates - childLocation));
 
-bool RenderBlock::relayoutForPagination(bool hasSpecifiedPageLogicalHeight, LayoutUnit pageLogicalHeight, LayoutStateMaintainer& statePusher)
-{
-    if (!hasColumns())
-        return false;
+    // If this is an anonymous renderer, we just recur normally
+    Element* childElement= child.nonPseudoElement();
+    if (!childElement)
+        return child.positionForPoint(pointInChildCoordinates, nullptr);
 
-    OwnPtr<RenderOverflow> savedOverflow = m_overflow.release();
-    if (childrenInline())
-        addOverflowFromInlineChildren();
-    else
-        addOverflowFromBlockChildren();
-    LayoutUnit layoutOverflowLogicalBottom = (isHorizontalWritingMode() ? layoutOverflowRect().maxY() : layoutOverflowRect().maxX()) - borderAndPaddingBefore();
-
-    // FIXME: We don't balance properly at all in the presence of forced page breaks.  We need to understand what
-    // the distance between forced page breaks is so that we can avoid making the minimum column height too tall.
-    ColumnInfo* colInfo = columnInfo();
-    if (!hasSpecifiedPageLogicalHeight) {
-        LayoutUnit columnHeight = pageLogicalHeight;
-        int minColumnCount = colInfo->forcedBreaks() + 1;
-        int desiredColumnCount = colInfo->desiredColumnCount();
-        if (minColumnCount >= desiredColumnCount) {
-            // The forced page breaks are in control of the balancing.  Just set the column height to the
-            // maximum page break distance.
-            if (!pageLogicalHeight) {
-                LayoutUnit distanceBetweenBreaks = max<LayoutUnit>(colInfo->maximumDistanceBetweenForcedBreaks(),
-                    view()->layoutState()->pageLogicalOffset(this, borderAndPaddingBefore() + layoutOverflowLogicalBottom) - colInfo->forcedBreakOffset());
-                columnHeight = max(colInfo->minimumColumnHeight(), distanceBetweenBreaks);
-            }
-        } else if (layoutOverflowLogicalBottom > boundedMultiply(pageLogicalHeight, desiredColumnCount)) {
-            // Now that we know the intrinsic height of the columns, we have to rebalance them.
-            columnHeight = max<LayoutUnit>(colInfo->minimumColumnHeight(), ceilf((float)layoutOverflowLogicalBottom / desiredColumnCount));
-        }
-        
-        if (columnHeight && columnHeight != pageLogicalHeight) {
-            statePusher.pop();
-            setEverHadLayout(true);
-            layoutBlock(false, columnHeight);
-            return true;
-        }
-    } 
+    // Otherwise, first make sure that the editability of the parent and child agree.
+    // If they don't agree, then we return a visible position just before or after the child
+    RenderElement* ancestor = &parent;
+    while (ancestor && !ancestor->nonPseudoElement())
+        ancestor = ancestor->parent();
 
-    if (pageLogicalHeight)
-        colInfo->setColumnCountAndHeight(ceilf((float)layoutOverflowLogicalBottom / pageLogicalHeight), pageLogicalHeight);
+    // If we can't find an ancestor to check editability on, or editability is unchanged, we recur like normal
+    if (isEditingBoundary(ancestor, child))
+        return child.positionForPoint(pointInChildCoordinates, nullptr);
 
-    if (columnCount(colInfo)) {
-        setLogicalHeight(borderAndPaddingBefore() + colInfo->columnHeight() + borderAndPaddingAfter() + scrollbarLogicalHeight());
-        m_overflow.clear();
-    } else
-        m_overflow = savedOverflow.release();
-    
-    return false;
+    // Otherwise return before or after the child, depending on if the click was to the logical left or logical right of the child
+    LayoutUnit childMiddle = parent.logicalWidthForChild(child) / 2;
+    LayoutUnit logicalLeft = parent.isHorizontalWritingMode() ? pointInChildCoordinates.x() : pointInChildCoordinates.y();
+    if (logicalLeft < childMiddle)
+        return ancestor->createVisiblePosition(childElement->computeNodeIndex(), DOWNSTREAM);
+    return ancestor->createVisiblePosition(childElement->computeNodeIndex() + 1, UPSTREAM);
 }
 
-void RenderBlock::adjustPointToColumnContents(LayoutPoint& point) const
+VisiblePosition RenderBlock::positionForPointWithInlineChildren(const LayoutPoint&, const RenderRegion*)
 {
-    // Just bail if we have no columns.
-    if (!hasColumns())
-        return;
-    
-    ColumnInfo* colInfo = columnInfo();
-    if (!columnCount(colInfo))
-        return;
+    ASSERT_NOT_REACHED();
+    return VisiblePosition();
+}
 
-    // Determine which columns we intersect.
-    LayoutUnit colGap = columnGap();
-    LayoutUnit halfColGap = colGap / 2;
-    LayoutPoint columnPoint(columnRectAt(colInfo, 0).location());
-    LayoutUnit logicalOffset = 0;
-    for (unsigned i = 0; i < colInfo->columnCount(); i++) {
-        // Add in half the column gap to the left and right of the rect.
-        LayoutRect colRect = columnRectAt(colInfo, i);
-        flipForWritingMode(colRect);
-        if (isHorizontalWritingMode() == (colInfo->progressionAxis() == ColumnInfo::InlineAxis)) {
-            LayoutRect gapAndColumnRect(colRect.x() - halfColGap, colRect.y(), colRect.width() + colGap, colRect.height());
-            if (point.x() >= gapAndColumnRect.x() && point.x() < gapAndColumnRect.maxX()) {
-                if (colInfo->progressionAxis() == ColumnInfo::InlineAxis) {
-                    // FIXME: The clamping that follows is not completely right for right-to-left
-                    // content.
-                    // Clamp everything above the column to its top left.
-                    if (point.y() < gapAndColumnRect.y())
-                        point = gapAndColumnRect.location();
-                    // Clamp everything below the column to the next column's top left. If there is
-                    // no next column, this still maps to just after this column.
-                    else if (point.y() >= gapAndColumnRect.maxY()) {
-                        point = gapAndColumnRect.location();
-                        point.move(0, gapAndColumnRect.height());
-                    }
-                } else {
-                    if (point.x() < colRect.x())
-                        point.setX(colRect.x());
-                    else if (point.x() >= colRect.maxX())
-                        point.setX(colRect.maxX() - 1);
-                }
+static inline bool isChildHitTestCandidate(const RenderBox& box)
+{
+    return box.height() && box.style().visibility() == VISIBLE && !box.isFloatingOrOutOfFlowPositioned() && !box.isInFlowRenderFlowThread();
+}
 
-                // We're inside the column.  Translate the x and y into our column coordinate space.
-                if (colInfo->progressionAxis() == ColumnInfo::InlineAxis)
-                    point.move(columnPoint.x() - colRect.x(), (!style()->isFlippedBlocksWritingMode() ? logicalOffset : -logicalOffset));
-                else
-                    point.move((!style()->isFlippedBlocksWritingMode() ? logicalOffset : -logicalOffset) - colRect.x() + borderLeft() + paddingLeft(), 0);
-                return;
-            }
+// Valid candidates in a FlowThread must be rendered by the region.
+static inline bool isChildHitTestCandidate(const RenderBox& box, const RenderRegion* region, const LayoutPoint& point)
+{
+    if (!isChildHitTestCandidate(box))
+        return false;
+    if (!region)
+        return true;
+    const RenderBlock& block = is<RenderBlock>(box) ? downcast<RenderBlock>(box) : *box.containingBlock();
+    return block.regionAtBlockOffset(point.y()) == region;
+}
 
-            // Move to the next position.
-            logicalOffset += colInfo->progressionAxis() == ColumnInfo::InlineAxis ? colRect.height() : colRect.width();
-        } else {
-            LayoutRect gapAndColumnRect(colRect.x(), colRect.y() - halfColGap, colRect.width(), colRect.height() + colGap);
-            if (point.y() >= gapAndColumnRect.y() && point.y() < gapAndColumnRect.maxY()) {
-                if (colInfo->progressionAxis() == ColumnInfo::InlineAxis) {
-                    // FIXME: The clamping that follows is not completely right for right-to-left
-                    // content.
-                    // Clamp everything above the column to its top left.
-                    if (point.x() < gapAndColumnRect.x())
-                        point = gapAndColumnRect.location();
-                    // Clamp everything below the column to the next column's top left. If there is
-                    // no next column, this still maps to just after this column.
-                    else if (point.x() >= gapAndColumnRect.maxX()) {
-                        point = gapAndColumnRect.location();
-                        point.move(gapAndColumnRect.width(), 0);
-                    }
-                } else {
-                    if (point.y() < colRect.y())
-                        point.setY(colRect.y());
-                    else if (point.y() >= colRect.maxY())
-                        point.setY(colRect.maxY() - 1);
-                }
+VisiblePosition RenderBlock::positionForPoint(const LayoutPoint& point, const RenderRegion* region)
+{
+    if (isTable())
+        return RenderBox::positionForPoint(point, region);
 
-                // We're inside the column.  Translate the x and y into our column coordinate space.
-                if (colInfo->progressionAxis() == ColumnInfo::InlineAxis)
-                    point.move((!style()->isFlippedBlocksWritingMode() ? logicalOffset : -logicalOffset), columnPoint.y() - colRect.y());
-                else
-                    point.move(0, (!style()->isFlippedBlocksWritingMode() ? logicalOffset : -logicalOffset) - colRect.y() + borderTop() + paddingTop());
-                return;
-            }
+    if (isReplaced()) {
+        // FIXME: This seems wrong when the object's writing-mode doesn't match the line's writing-mode.
+        LayoutUnit pointLogicalLeft = isHorizontalWritingMode() ? point.x() : point.y();
+        LayoutUnit pointLogicalTop = isHorizontalWritingMode() ? point.y() : point.x();
 
-            // Move to the next position.
-            logicalOffset += colInfo->progressionAxis() == ColumnInfo::InlineAxis ? colRect.width() : colRect.height();
-        }
-    }
-}
+        if (pointLogicalTop < 0 || (pointLogicalTop < logicalHeight() && pointLogicalLeft < 0))
+            return createVisiblePosition(caretMinOffset(), DOWNSTREAM);
+        if (pointLogicalTop >= logicalHeight() || (pointLogicalTop >= 0 && pointLogicalLeft >= logicalWidth()))
+            return createVisiblePosition(caretMaxOffset(), DOWNSTREAM);
+    } 
 
-void RenderBlock::adjustRectForColumns(LayoutRect& r) const
-{
-    // Just bail if we have no columns.
-    if (!hasColumns())
-        return;
-    
-    ColumnInfo* colInfo = columnInfo();
-    
-    // Determine which columns we intersect.
-    unsigned colCount = columnCount(colInfo);
-    if (!colCount)
-        return;
+    LayoutPoint pointInContents = point;
+    offsetForContents(pointInContents);
+    LayoutPoint pointInLogicalContents(pointInContents);
+    if (!isHorizontalWritingMode())
+        pointInLogicalContents = pointInLogicalContents.transposedPoint();
 
-    // Begin with a result rect that is empty.
-    LayoutRect result;
+    if (childrenInline())
+        return positionForPointWithInlineChildren(pointInLogicalContents, region);
 
-    bool isHorizontal = isHorizontalWritingMode();
-    LayoutUnit beforeBorderPadding = borderAndPaddingBefore();
-    LayoutUnit colHeight = colInfo->columnHeight();
-    if (!colHeight)
-        return;
+    RenderBox* lastCandidateBox = lastChildBox();
 
-    LayoutUnit startOffset = max(isHorizontal ? r.y() : r.x(), beforeBorderPadding);
-    LayoutUnit endOffset = max(min<LayoutUnit>(isHorizontal ? r.maxY() : r.maxX(), beforeBorderPadding + colCount * colHeight), beforeBorderPadding);
+    if (!region)
+        region = regionAtBlockOffset(pointInLogicalContents.y());
 
-    // FIXME: Can overflow on fast/block/float/float-not-removed-from-next-sibling4.html, see https://bugs.webkit.org/show_bug.cgi?id=68744
-    unsigned startColumn = (startOffset - beforeBorderPadding) / colHeight;
-    unsigned endColumn = (endOffset - beforeBorderPadding) / colHeight;
+    while (lastCandidateBox && !isChildHitTestCandidate(*lastCandidateBox, region, pointInLogicalContents))
+        lastCandidateBox = lastCandidateBox->previousSiblingBox();
 
-    if (startColumn == endColumn) {
-        // The rect is fully contained within one column. Adjust for our offsets
-        // and repaint only that portion.
-        LayoutUnit logicalLeftOffset = logicalLeftOffsetForContent();
-        LayoutRect colRect = columnRectAt(colInfo, startColumn);
-        LayoutRect repaintRect = r;
+    bool blocksAreFlipped = style().isFlippedBlocksWritingMode();
+    if (lastCandidateBox) {
+        if (pointInLogicalContents.y() > logicalTopForChild(*lastCandidateBox)
+            || (!blocksAreFlipped && pointInLogicalContents.y() == logicalTopForChild(*lastCandidateBox)))
+            return positionForPointRespectingEditingBoundaries(*this, *lastCandidateBox, pointInContents);
 
-        if (colInfo->progressionAxis() == ColumnInfo::InlineAxis) {
-            if (isHorizontal)
-                repaintRect.move(colRect.x() - logicalLeftOffset, - static_cast<int>(startColumn) * colHeight);
-            else
-                repaintRect.move(- static_cast<int>(startColumn) * colHeight, colRect.y() - logicalLeftOffset);
-        } else {
-            if (isHorizontal)
-                repaintRect.move(0, colRect.y() - startColumn * colHeight - beforeBorderPadding);
-            else
-                repaintRect.move(colRect.x() - startColumn * colHeight - beforeBorderPadding, 0);
+        for (auto* childBox = firstChildBox(); childBox; childBox = childBox->nextSiblingBox()) {
+            if (!isChildHitTestCandidate(*childBox, region, pointInLogicalContents))
+                continue;
+            LayoutUnit childLogicalBottom = logicalTopForChild(*childBox) + logicalHeightForChild(*childBox);
+            // We hit child if our click is above the bottom of its padding box (like IE6/7 and FF3).
+            if (isChildHitTestCandidate(*childBox, region, pointInLogicalContents) && (pointInLogicalContents.y() < childLogicalBottom
+                || (blocksAreFlipped && pointInLogicalContents.y() == childLogicalBottom)))
+                return positionForPointRespectingEditingBoundaries(*this, *childBox, pointInContents);
         }
-        repaintRect.intersect(colRect);
-        result.unite(repaintRect);
-    } else {
-        // We span multiple columns. We can just unite the start and end column to get the final
-        // repaint rect.
-        result.unite(columnRectAt(colInfo, startColumn));
-        result.unite(columnRectAt(colInfo, endColumn));
     }
 
-    r = result;
-}
-
-LayoutPoint RenderBlock::flipForWritingModeIncludingColumns(const LayoutPoint& point) const
-{
-    ASSERT(hasColumns());
-    if (!hasColumns() || !style()->isFlippedBlocksWritingMode())
-        return point;
-    ColumnInfo* colInfo = columnInfo();
-    LayoutUnit columnLogicalHeight = colInfo->columnHeight();
-    LayoutUnit expandedLogicalHeight = borderAndPaddingBefore() + columnCount(colInfo) * columnLogicalHeight + borderAndPaddingAfter() + scrollbarLogicalHeight();
-    if (isHorizontalWritingMode())
-        return LayoutPoint(point.x(), expandedLogicalHeight - point.y());
-    return LayoutPoint(expandedLogicalHeight - point.x(), point.y());
-}
-
-void RenderBlock::adjustStartEdgeForWritingModeIncludingColumns(LayoutRect& rect) const
-{
-    ASSERT(hasColumns());
-    if (!hasColumns() || !style()->isFlippedBlocksWritingMode())
-        return;
-    
-    ColumnInfo* colInfo = columnInfo();
-    LayoutUnit columnLogicalHeight = colInfo->columnHeight();
-    LayoutUnit expandedLogicalHeight = borderAndPaddingBefore() + columnCount(colInfo) * columnLogicalHeight + borderAndPaddingAfter() + scrollbarLogicalHeight();
-    
-    if (isHorizontalWritingMode())
-        rect.setY(expandedLogicalHeight - rect.maxY());
-    else
-        rect.setX(expandedLogicalHeight - rect.maxX());
+    // We only get here if there are no hit test candidate children below the click.
+    return RenderBox::positionForPoint(point, region);
 }
 
-void RenderBlock::adjustForColumns(LayoutSize& offset, const LayoutPoint& point) const
+void RenderBlock::offsetForContents(LayoutPoint& offset) const
 {
-    if (!hasColumns())
-        return;
-
-    ColumnInfo* colInfo = columnInfo();
-
-    LayoutUnit logicalLeft = logicalLeftOffsetForContent();
-    unsigned colCount = columnCount(colInfo);
-    LayoutUnit colLogicalWidth = colInfo->desiredColumnWidth();
-    LayoutUnit colLogicalHeight = colInfo->columnHeight();
-
-    for (unsigned i = 0; i < colCount; ++i) {
-        // Compute the edges for a given column in the block progression direction.
-        LayoutRect sliceRect = LayoutRect(logicalLeft, borderAndPaddingBefore() + i * colLogicalHeight, colLogicalWidth, colLogicalHeight);
-        if (!isHorizontalWritingMode())
-            sliceRect = sliceRect.transposedRect();
-        
-        LayoutUnit logicalOffset = i * colLogicalHeight;
-
-        // Now we're in the same coordinate space as the point.  See if it is inside the rectangle.
-        if (isHorizontalWritingMode()) {
-            if (point.y() >= sliceRect.y() && point.y() < sliceRect.maxY()) {
-                if (colInfo->progressionAxis() == ColumnInfo::InlineAxis)
-                    offset.expand(columnRectAt(colInfo, i).x() - logicalLeft, -logicalOffset);
-                else
-                    offset.expand(0, columnRectAt(colInfo, i).y() - logicalOffset - borderAndPaddingBefore());
-                return;
-            }
-        } else {
-            if (point.x() >= sliceRect.x() && point.x() < sliceRect.maxX()) {
-                if (colInfo->progressionAxis() == ColumnInfo::InlineAxis)
-                    offset.expand(-logicalOffset, columnRectAt(colInfo, i).y() - logicalLeft);
-                else
-                    offset.expand(columnRectAt(colInfo, i).x() - logicalOffset - borderAndPaddingBefore(), 0);
-                return;
-            }
-        }
-    }
+    offset = flipForWritingMode(offset);
+    offset += scrolledContentOffset();
+    offset = flipForWritingMode(offset);
 }
 
 void RenderBlock::computeIntrinsicLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const
 {
-    if (childrenInline()) {
-        // FIXME: Remove this const_cast.
-        const_cast<RenderBlock*>(this)->computeInlinePreferredLogicalWidths(minLogicalWidth, maxLogicalWidth);
-    } else
-        computeBlockPreferredLogicalWidths(minLogicalWidth, maxLogicalWidth);
-
-    maxLogicalWidth = max(minLogicalWidth, maxLogicalWidth);
-
-    if (!style()->autoWrap() && childrenInline()) {
-        // A horizontal marquee with inline children has no minimum width.
-        if (layer() && layer()->marquee() && layer()->marquee()->isHorizontal())
-            minLogicalWidth = 0;
-    }
+    ASSERT(!childrenInline());
+    
+    computeBlockPreferredLogicalWidths(minLogicalWidth, maxLogicalWidth);
 
-    if (isTableCell()) {
-        Length tableCellWidth = toRenderTableCell(this)->styleOrColLogicalWidth();
-        if (tableCellWidth.isFixed() && tableCellWidth.value() > 0)
-            maxLogicalWidth = max(minLogicalWidth, adjustContentBoxLogicalWidthForBoxSizing(tableCellWidth.value()));
-    }
+    maxLogicalWidth = std::max(minLogicalWidth, maxLogicalWidth);
 
-    int scrollbarWidth = instrinsicScrollbarLogicalWidth();
+    int scrollbarWidth = intrinsicScrollbarLogicalWidth();
     maxLogicalWidth += scrollbarWidth;
     minLogicalWidth += scrollbarWidth;
 }
@@ -5953,29 +2690,23 @@ void RenderBlock::computePreferredLogicalWidths()
     m_minPreferredLogicalWidth = 0;
     m_maxPreferredLogicalWidth = 0;
 
-    RenderStyle* styleToUse = style();
-    if (!isTableCell() && styleToUse->logicalWidth().isFixed() && styleToUse->logicalWidth().value() >= 0 
-        && !(isDeprecatedFlexItem() && !styleToUse->logicalWidth().intValue()))
-        m_minPreferredLogicalWidth = m_maxPreferredLogicalWidth = adjustContentBoxLogicalWidthForBoxSizing(styleToUse->logicalWidth().value());
+    const RenderStyle& styleToUse = style();
+    if (!isTableCell() && styleToUse.logicalWidth().isFixed() && styleToUse.logicalWidth().value() >= 0
+        && !(isDeprecatedFlexItem() && !styleToUse.logicalWidth().intValue()))
+        m_minPreferredLogicalWidth = m_maxPreferredLogicalWidth = adjustContentBoxLogicalWidthForBoxSizing(styleToUse.logicalWidth().value());
     else
         computeIntrinsicLogicalWidths(m_minPreferredLogicalWidth, m_maxPreferredLogicalWidth);
     
-    if (styleToUse->logicalMinWidth().isFixed() && styleToUse->logicalMinWidth().value() > 0) {
-        m_maxPreferredLogicalWidth = max(m_maxPreferredLogicalWidth, adjustContentBoxLogicalWidthForBoxSizing(styleToUse->logicalMinWidth().value()));
-        m_minPreferredLogicalWidth = max(m_minPreferredLogicalWidth, adjustContentBoxLogicalWidthForBoxSizing(styleToUse->logicalMinWidth().value()));
+    if (styleToUse.logicalMinWidth().isFixed() && styleToUse.logicalMinWidth().value() > 0) {
+        m_maxPreferredLogicalWidth = std::max(m_maxPreferredLogicalWidth, adjustContentBoxLogicalWidthForBoxSizing(styleToUse.logicalMinWidth().value()));
+        m_minPreferredLogicalWidth = std::max(m_minPreferredLogicalWidth, adjustContentBoxLogicalWidthForBoxSizing(styleToUse.logicalMinWidth().value()));
     }
     
-    if (styleToUse->logicalMaxWidth().isFixed()) {
-        m_maxPreferredLogicalWidth = min(m_maxPreferredLogicalWidth, adjustContentBoxLogicalWidthForBoxSizing(styleToUse->logicalMaxWidth().value()));
-        m_minPreferredLogicalWidth = min(m_minPreferredLogicalWidth, adjustContentBoxLogicalWidthForBoxSizing(styleToUse->logicalMaxWidth().value()));
+    if (styleToUse.logicalMaxWidth().isFixed()) {
+        m_maxPreferredLogicalWidth = std::min(m_maxPreferredLogicalWidth, adjustContentBoxLogicalWidthForBoxSizing(styleToUse.logicalMaxWidth().value()));
+        m_minPreferredLogicalWidth = std::min(m_minPreferredLogicalWidth, adjustContentBoxLogicalWidthForBoxSizing(styleToUse.logicalMaxWidth().value()));
     }
     
-    // Table layout uses integers, ceil the preferred widths to ensure that they can contain the contents.
-    if (isTableCell()) {
-        m_minPreferredLogicalWidth = m_minPreferredLogicalWidth.ceil();
-        m_maxPreferredLogicalWidth = m_maxPreferredLogicalWidth.ceil();
-    }
-
     LayoutUnit borderAndPadding = borderAndPaddingLogicalWidth();
     m_minPreferredLogicalWidth += borderAndPadding;
     m_maxPreferredLogicalWidth += borderAndPadding;
@@ -5983,435 +2714,10 @@ void RenderBlock::computePreferredLogicalWidths()
     setPreferredLogicalWidthsDirty(false);
 }
 
-struct InlineMinMaxIterator {
-/* InlineMinMaxIterator is a class that will iterate over all render objects that contribute to
-   inline min/max width calculations.  Note the following about the way it walks:
-   (1) Positioned content is skipped (since it does not contribute to min/max width of a block)
-   (2) We do not drill into the children of floats or replaced elements, since you can't break
-       in the middle of such an element.
-   (3) Inline flows (e.g., <a>, <span>, <i>) are walked twice, since each side can have
-       distinct borders/margin/padding that contribute to the min/max width.
-*/
-    RenderObject* parent;
-    RenderObject* current;
-    bool endOfInline;
-
-    InlineMinMaxIterator(RenderObject* p, bool end = false)
-        :parent(p), current(p), endOfInline(end) {}
-
-    RenderObject* next();
-};
-
-RenderObject* InlineMinMaxIterator::next()
-{
-    RenderObject* result = 0;
-    bool oldEndOfInline = endOfInline;
-    endOfInline = false;
-    while (current || current == parent) {
-        if (!oldEndOfInline &&
-            (current == parent ||
-             (!current->isFloating() && !current->isReplaced() && !current->isOutOfFlowPositioned())))
-            result = current->firstChild();
-        if (!result) {
-            // We hit the end of our inline. (It was empty, e.g., <span></span>.)
-            if (!oldEndOfInline && current->isRenderInline()) {
-                result = current;
-                endOfInline = true;
-                break;
-            }
-
-            while (current && current != parent) {
-                result = current->nextSibling();
-                if (result) break;
-                current = current->parent();
-                if (current && current != parent && current->isRenderInline()) {
-                    result = current;
-                    endOfInline = true;
-                    break;
-                }
-            }
-        }
-
-        if (!result)
-            break;
-
-        if (!result->isOutOfFlowPositioned() && (result->isText() || result->isFloating() || result->isReplaced() || result->isRenderInline()))
-             break;
-        
-        current = result;
-        result = 0;
-    }
-
-    // Update our position.
-    current = result;
-    return current;
-}
-
-static LayoutUnit getBPMWidth(LayoutUnit childValue, Length cssUnit)
-{
-    if (cssUnit.type() != Auto)
-        return (cssUnit.isFixed() ? static_cast<LayoutUnit>(cssUnit.value()) : childValue);
-    return 0;
-}
-
-static LayoutUnit getBorderPaddingMargin(const RenderBoxModelObject* child, bool endOfInline)
-{
-    RenderStyle* childStyle = child->style();
-    if (endOfInline)
-        return getBPMWidth(child->marginEnd(), childStyle->marginEnd()) +
-               getBPMWidth(child->paddingEnd(), childStyle->paddingEnd()) +
-               child->borderEnd();
-    return getBPMWidth(child->marginStart(), childStyle->marginStart()) +
-               getBPMWidth(child->paddingStart(), childStyle->paddingStart()) +
-               child->borderStart();
-}
-
-static inline void stripTrailingSpace(float& inlineMax, float& inlineMin,
-                                      RenderObject* trailingSpaceChild)
-{
-    if (trailingSpaceChild && trailingSpaceChild->isText()) {
-        // Collapse away the trailing space at the end of a block.
-        RenderText* t = toRenderText(trailingSpaceChild);
-        const UChar space = ' ';
-        const Font& font = t->style()->font(); // FIXME: This ignores first-line.
-        float spaceWidth = font.width(RenderBlock::constructTextRun(t, font, &space, 1, t->style()));
-        inlineMax -= spaceWidth + font.wordSpacing();
-        if (inlineMin > inlineMax)
-            inlineMin = inlineMax;
-    }
-}
-
-static inline void updatePreferredWidth(LayoutUnit& preferredWidth, float& result)
-{
-    LayoutUnit snappedResult = ceiledLayoutUnit(result);
-    preferredWidth = max(snappedResult, preferredWidth);
-}
-
-// With sub-pixel enabled: When converting between floating point and LayoutUnits
-// we risk losing precision with each conversion. When this occurs while
-// accumulating our preferred widths, we can wind up with a line width that's
-// larger than our maxPreferredWidth due to pure float accumulation.
-//
-// With sub-pixel disabled: values from Lengths or the render tree aren't subject
-// to the same loss of precision, as they're always truncated and stored as
-// integers. We mirror that behavior here to prevent over-allocating our preferred
-// width.
-static inline LayoutUnit adjustFloatForSubPixelLayout(float value)
-{
-#if ENABLE(SUBPIXEL_LAYOUT)
-    return ceiledLayoutUnit(value);
-#else
-    return static_cast<int>(value);
-#endif
-}
-
-
-void RenderBlock::computeInlinePreferredLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth)
-{
-    float inlineMax = 0;
-    float inlineMin = 0;
-
-    RenderStyle* styleToUse = style();
-    RenderBlock* containingBlock = this->containingBlock();
-    LayoutUnit cw = containingBlock ? containingBlock->contentLogicalWidth() : LayoutUnit();
-
-    // If we are at the start of a line, we want to ignore all white-space.
-    // Also strip spaces if we previously had text that ended in a trailing space.
-    bool stripFrontSpaces = true;
-    RenderObject* trailingSpaceChild = 0;
-
-    // Firefox and Opera will allow a table cell to grow to fit an image inside it under
-    // very specific cirucumstances (in order to match common WinIE renderings). 
-    // Not supporting the quirk has caused us to mis-render some real sites. (See Bugzilla 10517.) 
-    bool allowImagesToBreak = !document()->inQuirksMode() || !isTableCell() || !styleToUse->logicalWidth().isIntrinsicOrAuto();
-
-    bool autoWrap, oldAutoWrap;
-    autoWrap = oldAutoWrap = styleToUse->autoWrap();
-
-    InlineMinMaxIterator childIterator(this);
-
-    // Only gets added to the max preffered width once.
-    bool addedTextIndent = false;
-    // Signals the text indent was more negative than the min preferred width
-    bool hasRemainingNegativeTextIndent = false;
-
-    LayoutUnit textIndent = minimumValueForLength(styleToUse->textIndent(), cw, view());
-    RenderObject* prevFloat = 0;
-    bool isPrevChildInlineFlow = false;
-    bool shouldBreakLineAfterText = false;
-    while (RenderObject* child = childIterator.next()) {
-        autoWrap = child->isReplaced() ? child->parent()->style()->autoWrap() : 
-            child->style()->autoWrap();
-
-        if (!child->isBR()) {
-            // Step One: determine whether or not we need to go ahead and
-            // terminate our current line.  Each discrete chunk can become
-            // the new min-width, if it is the widest chunk seen so far, and
-            // it can also become the max-width.
-
-            // Children fall into three categories:
-            // (1) An inline flow object.  These objects always have a min/max of 0,
-            // and are included in the iteration solely so that their margins can
-            // be added in.
-            //
-            // (2) An inline non-text non-flow object, e.g., an inline replaced element.
-            // These objects can always be on a line by themselves, so in this situation
-            // we need to go ahead and break the current line, and then add in our own
-            // margins and min/max width on its own line, and then terminate the line.
-            //
-            // (3) A text object.  Text runs can have breakable characters at the start,
-            // the middle or the end.  They may also lose whitespace off the front if
-            // we're already ignoring whitespace.  In order to compute accurate min-width
-            // information, we need three pieces of information.
-            // (a) the min-width of the first non-breakable run.  Should be 0 if the text string
-            // starts with whitespace.
-            // (b) the min-width of the last non-breakable run. Should be 0 if the text string
-            // ends with whitespace.
-            // (c) the min/max width of the string (trimmed for whitespace).
-            //
-            // If the text string starts with whitespace, then we need to go ahead and
-            // terminate our current line (unless we're already in a whitespace stripping
-            // mode.
-            //
-            // If the text string has a breakable character in the middle, but didn't start
-            // with whitespace, then we add the width of the first non-breakable run and
-            // then end the current line.  We then need to use the intermediate min/max width
-            // values (if any of them are larger than our current min/max).  We then look at
-            // the width of the last non-breakable run and use that to start a new line
-            // (unless we end in whitespace).
-            RenderStyle* childStyle = child->style();
-            float childMin = 0;
-            float childMax = 0;
-
-            if (!child->isText()) {
-                // Case (1) and (2).  Inline replaced and inline flow elements.
-                if (child->isRenderInline()) {
-                    // Add in padding/border/margin from the appropriate side of
-                    // the element.
-                    float bpm = getBorderPaddingMargin(toRenderInline(child), childIterator.endOfInline);
-                    childMin += bpm;
-                    childMax += bpm;
-
-                    inlineMin += childMin;
-                    inlineMax += childMax;
-                    
-                    child->setPreferredLogicalWidthsDirty(false);
-                } else {
-                    // Inline replaced elts add in their margins to their min/max values.
-                    LayoutUnit margins = 0;
-                    Length startMargin = childStyle->marginStart();
-                    Length endMargin = childStyle->marginEnd();
-                    if (startMargin.isFixed())
-                        margins += adjustFloatForSubPixelLayout(startMargin.value());
-                    if (endMargin.isFixed())
-                        margins += adjustFloatForSubPixelLayout(endMargin.value());
-                    childMin += margins.ceilToFloat();
-                    childMax += margins.ceilToFloat();
-                }
-            }
-
-            if (!child->isRenderInline() && !child->isText()) {
-                // Case (2). Inline replaced elements and floats.
-                // Go ahead and terminate the current line as far as
-                // minwidth is concerned.
-                childMin += child->minPreferredLogicalWidth().ceilToFloat();
-                childMax += child->maxPreferredLogicalWidth().ceilToFloat();
-
-                bool clearPreviousFloat;
-                if (child->isFloating()) {
-                    clearPreviousFloat = (prevFloat
-                        && ((prevFloat->style()->floating() == LeftFloat && (childStyle->clear() & CLEFT))
-                            || (prevFloat->style()->floating() == RightFloat && (childStyle->clear() & CRIGHT))));
-                    prevFloat = child;
-                } else
-                    clearPreviousFloat = false;
-
-                bool canBreakReplacedElement = !child->isImage() || allowImagesToBreak;
-                if ((canBreakReplacedElement && (autoWrap || oldAutoWrap) && (!isPrevChildInlineFlow || shouldBreakLineAfterText)) || clearPreviousFloat) {
-                    updatePreferredWidth(minLogicalWidth, inlineMin);
-                    inlineMin = 0;
-                }
-
-                // If we're supposed to clear the previous float, then terminate maxwidth as well.
-                if (clearPreviousFloat) {
-                    updatePreferredWidth(maxLogicalWidth, inlineMax);
-                    inlineMax = 0;
-                }
-
-                // Add in text-indent.  This is added in only once.
-                if (!addedTextIndent && !child->isFloating()) {
-                    LayoutUnit ceiledIndent = textIndent.ceilToFloat();
-                    childMin += ceiledIndent;
-                    childMax += ceiledIndent;
-
-                    if (childMin < 0)
-                        textIndent = adjustFloatForSubPixelLayout(childMin);
-                    else
-                        addedTextIndent = true;
-                }
-
-                // Add our width to the max.
-                inlineMax += max<float>(0, childMax);
-
-                if (!autoWrap || !canBreakReplacedElement || (isPrevChildInlineFlow && !shouldBreakLineAfterText)) {
-                    if (child->isFloating())
-                        updatePreferredWidth(minLogicalWidth, childMin);
-                    else
-                        inlineMin += childMin;
-                } else {
-                    // Now check our line.
-                    updatePreferredWidth(minLogicalWidth, childMin);
-
-                    // Now start a new line.
-                    inlineMin = 0;
-                }
-
-                if (autoWrap && canBreakReplacedElement && isPrevChildInlineFlow) {
-                    updatePreferredWidth(minLogicalWidth, inlineMin);
-                    inlineMin = 0;
-                }
-
-                // We are no longer stripping whitespace at the start of
-                // a line.
-                if (!child->isFloating()) {
-                    stripFrontSpaces = false;
-                    trailingSpaceChild = 0;
-                }
-            } else if (child->isText()) {
-                // Case (3). Text.
-                RenderText* t = toRenderText(child);
-
-                if (t->isWordBreak()) {
-                    updatePreferredWidth(minLogicalWidth, inlineMin);
-                    inlineMin = 0;
-                    continue;
-                }
-
-                if (t->style()->hasTextCombine() && t->isCombineText())
-                    toRenderCombineText(t)->combineText();
-
-                // Determine if we have a breakable character.  Pass in
-                // whether or not we should ignore any spaces at the front
-                // of the string.  If those are going to be stripped out,
-                // then they shouldn't be considered in the breakable char
-                // check.
-                bool hasBreakableChar, hasBreak;
-                float beginMin, endMin;
-                bool beginWS, endWS;
-                float beginMax, endMax;
-                t->trimmedPrefWidths(inlineMax, beginMin, beginWS, endMin, endWS,
-                                     hasBreakableChar, hasBreak, beginMax, endMax,
-                                     childMin, childMax, stripFrontSpaces);
-
-                // This text object will not be rendered, but it may still provide a breaking opportunity.
-                if (!hasBreak && childMax == 0) {
-                    if (autoWrap && (beginWS || endWS)) {
-                        updatePreferredWidth(minLogicalWidth, inlineMin);
-                        inlineMin = 0;
-                    }
-                    continue;
-                }
-                
-                if (stripFrontSpaces)
-                    trailingSpaceChild = child;
-                else
-                    trailingSpaceChild = 0;
-
-                // Add in text-indent.  This is added in only once.
-                float ti = 0;
-                if (!addedTextIndent || hasRemainingNegativeTextIndent) {
-                    ti = textIndent.ceilToFloat();
-                    childMin += ti;
-                    beginMin += ti;
-                    
-                    // It the text indent negative and larger than the child minimum, we re-use the remainder
-                    // in future minimum calculations, but using the negative value again on the maximum
-                    // will lead to under-counting the max pref width.
-                    if (!addedTextIndent) {
-                        childMax += ti;
-                        beginMax += ti;
-                        addedTextIndent = true;
-                    }
-                    
-                    if (childMin < 0) {
-                        textIndent = childMin;
-                        hasRemainingNegativeTextIndent = true;
-                    }
-                }
-                
-                // If we have no breakable characters at all,
-                // then this is the easy case. We add ourselves to the current
-                // min and max and continue.
-                if (!hasBreakableChar) {
-                    inlineMin += childMin;
-                } else {
-                    // We have a breakable character.  Now we need to know if
-                    // we start and end with whitespace.
-                    if (beginWS)
-                        // Go ahead and end the current line.
-                        updatePreferredWidth(minLogicalWidth, inlineMin);
-                    else {
-                        inlineMin += beginMin;
-                        updatePreferredWidth(minLogicalWidth, inlineMin);
-                        childMin -= ti;
-                    }
-
-                    inlineMin = childMin;
-
-                    if (endWS) {
-                        // We end in whitespace, which means we can go ahead
-                        // and end our current line.
-                        updatePreferredWidth(minLogicalWidth, inlineMin);
-                        inlineMin = 0;
-                        shouldBreakLineAfterText = false;
-                    } else {
-                        updatePreferredWidth(minLogicalWidth, inlineMin);
-                        inlineMin = endMin;
-                        shouldBreakLineAfterText = true;
-                    }
-                }
-
-                if (hasBreak) {
-                    inlineMax += beginMax;
-                    updatePreferredWidth(maxLogicalWidth, inlineMax);
-                    updatePreferredWidth(maxLogicalWidth, childMax);
-                    inlineMax = endMax;
-                    addedTextIndent = true;
-                } else
-                    inlineMax += max<float>(0, childMax);
-            }
-
-            // Ignore spaces after a list marker.
-            if (child->isListMarker())
-                stripFrontSpaces = true;
-        } else {
-            updatePreferredWidth(minLogicalWidth, inlineMin);
-            updatePreferredWidth(maxLogicalWidth, inlineMax);
-            inlineMin = inlineMax = 0;
-            stripFrontSpaces = true;
-            trailingSpaceChild = 0;
-            addedTextIndent = true;
-        }
-
-        if (!child->isText() && child->isRenderInline())
-            isPrevChildInlineFlow = true;
-        else
-            isPrevChildInlineFlow = false;
-
-        oldAutoWrap = autoWrap;
-    }
-
-    if (styleToUse->collapseWhiteSpace())
-        stripTrailingSpace(inlineMax, inlineMin, trailingSpaceChild);
-
-    updatePreferredWidth(minLogicalWidth, inlineMin);
-    updatePreferredWidth(maxLogicalWidth, inlineMax);
-}
-
 void RenderBlock::computeBlockPreferredLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const
 {
-    RenderStyle* styleToUse = style();
-    bool nowrap = styleToUse->whiteSpace() == NOWRAP;
+    const RenderStyle& styleToUse = style();
+    bool nowrap = styleToUse.whiteSpace() == NOWRAP;
 
     RenderObject* child = firstChild();
     RenderBlock* containingBlock = this->containingBlock();
@@ -6423,15 +2729,15 @@ void RenderBlock::computeBlockPreferredLogicalWidths(LayoutUnit& minLogicalWidth
             continue;
         }
 
-        RenderStyle* childStyle = child->style();
-        if (child->isFloating() || (child->isBox() && toRenderBox(child)->avoidsFloats())) {
+        const RenderStyle& childStyle = child->style();
+        if (child->isFloating() || (is<RenderBox>(*child) && downcast<RenderBox>(*child).avoidsFloats())) {
             LayoutUnit floatTotalWidth = floatLeftWidth + floatRightWidth;
-            if (childStyle->clear() & CLEFT) {
-                maxLogicalWidth = max(floatTotalWidth, maxLogicalWidth);
+            if (childStyle.clear() & CLEFT) {
+                maxLogicalWidth = std::max(floatTotalWidth, maxLogicalWidth);
                 floatLeftWidth = 0;
             }
-            if (childStyle->clear() & CRIGHT) {
-                maxLogicalWidth = max(floatTotalWidth, maxLogicalWidth);
+            if (childStyle.clear() & CRIGHT) {
+                maxLogicalWidth = std::max(floatTotalWidth, maxLogicalWidth);
                 floatRightWidth = 0;
             }
         }
@@ -6439,8 +2745,8 @@ void RenderBlock::computeBlockPreferredLogicalWidths(LayoutUnit& minLogicalWidth
         // A margin basically has three types: fixed, percentage, and auto (variable).
         // Auto and percentage margins simply become 0 when computing min/max width.
         // Fixed margins can be added in as is.
-        Length startMarginLength = childStyle->marginStartUsing(styleToUse);
-        Length endMarginLength = childStyle->marginEndUsing(styleToUse);
+        Length startMarginLength = childStyle.marginStartUsing(&styleToUse);
+        Length endMarginLength = childStyle.marginEndUsing(&styleToUse);
         LayoutUnit margin = 0;
         LayoutUnit marginStart = 0;
         LayoutUnit marginEnd = 0;
@@ -6451,70 +2757,75 @@ void RenderBlock::computeBlockPreferredLogicalWidths(LayoutUnit& minLogicalWidth
         margin = marginStart + marginEnd;
 
         LayoutUnit childMinPreferredLogicalWidth, childMaxPreferredLogicalWidth;
-        if (child->isBox() && child->isHorizontalWritingMode() != isHorizontalWritingMode()) {
-            RenderBox* childBox = toRenderBox(child);
+        if (is<RenderBox>(*child) && child->isHorizontalWritingMode() != isHorizontalWritingMode()) {
+            auto& childBox = downcast<RenderBox>(*child);
             LogicalExtentComputedValues computedValues;
-            childBox->computeLogicalHeight(childBox->borderAndPaddingLogicalHeight(), 0, computedValues);
+            childBox.computeLogicalHeight(childBox.borderAndPaddingLogicalHeight(), 0, computedValues);
             childMinPreferredLogicalWidth = childMaxPreferredLogicalWidth = computedValues.m_extent;
         } else {
             childMinPreferredLogicalWidth = child->minPreferredLogicalWidth();
             childMaxPreferredLogicalWidth = child->maxPreferredLogicalWidth();
+
+            if (is<RenderBlock>(*child)) {
+                const Length& computedInlineSize = child->style().logicalWidth();
+                if (computedInlineSize.isMaxContent())
+                    childMinPreferredLogicalWidth = childMaxPreferredLogicalWidth;
+                else if (computedInlineSize.isMinContent())
+                    childMaxPreferredLogicalWidth = childMinPreferredLogicalWidth;
+            }
         }
 
         LayoutUnit w = childMinPreferredLogicalWidth + margin;
-        minLogicalWidth = max(w, minLogicalWidth);
+        minLogicalWidth = std::max(w, minLogicalWidth);
         
         // IE ignores tables for calculation of nowrap. Makes some sense.
         if (nowrap && !child->isTable())
-            maxLogicalWidth = max(w, maxLogicalWidth);
+            maxLogicalWidth = std::max(w, maxLogicalWidth);
 
         w = childMaxPreferredLogicalWidth + margin;
 
         if (!child->isFloating()) {
-            if (child->isBox() && toRenderBox(child)->avoidsFloats()) {
+            if (is<RenderBox>(*child) && downcast<RenderBox>(*child).avoidsFloats()) {
                 // Determine a left and right max value based off whether or not the floats can fit in the
                 // margins of the object.  For negative margins, we will attempt to overlap the float if the negative margin
                 // is smaller than the float width.
-                bool ltr = containingBlock ? containingBlock->style()->isLeftToRightDirection() : styleToUse->isLeftToRightDirection();
+                bool ltr = containingBlock ? containingBlock->style().isLeftToRightDirection() : styleToUse.isLeftToRightDirection();
                 LayoutUnit marginLogicalLeft = ltr ? marginStart : marginEnd;
                 LayoutUnit marginLogicalRight = ltr ? marginEnd : marginStart;
-                LayoutUnit maxLeft = marginLogicalLeft > 0 ? max(floatLeftWidth, marginLogicalLeft) : floatLeftWidth + marginLogicalLeft;
-                LayoutUnit maxRight = marginLogicalRight > 0 ? max(floatRightWidth, marginLogicalRight) : floatRightWidth + marginLogicalRight;
+                LayoutUnit maxLeft = marginLogicalLeft > 0 ? std::max(floatLeftWidth, marginLogicalLeft) : floatLeftWidth + marginLogicalLeft;
+                LayoutUnit maxRight = marginLogicalRight > 0 ? std::max(floatRightWidth, marginLogicalRight) : floatRightWidth + marginLogicalRight;
                 w = childMaxPreferredLogicalWidth + maxLeft + maxRight;
-                w = max(w, floatLeftWidth + floatRightWidth);
+                w = std::max(w, floatLeftWidth + floatRightWidth);
             }
             else
-                maxLogicalWidth = max(floatLeftWidth + floatRightWidth, maxLogicalWidth);
+                maxLogicalWidth = std::max(floatLeftWidth + floatRightWidth, maxLogicalWidth);
             floatLeftWidth = floatRightWidth = 0;
         }
         
         if (child->isFloating()) {
-            if (childStyle->floating() == LeftFloat)
+            if (childStyle.floating() == LeftFloat)
                 floatLeftWidth += w;
             else
                 floatRightWidth += w;
         } else
-            maxLogicalWidth = max(w, maxLogicalWidth);
+            maxLogicalWidth = std::max(w, maxLogicalWidth);
         
         child = child->nextSibling();
     }
 
     // Always make sure these values are non-negative.
-    minLogicalWidth = max<LayoutUnit>(0, minLogicalWidth);
-    maxLogicalWidth = max<LayoutUnit>(0, maxLogicalWidth);
+    minLogicalWidth = std::max<LayoutUnit>(0, minLogicalWidth);
+    maxLogicalWidth = std::max<LayoutUnit>(0, maxLogicalWidth);
 
-    maxLogicalWidth = max(floatLeftWidth + floatRightWidth, maxLogicalWidth);
+    maxLogicalWidth = std::max(floatLeftWidth + floatRightWidth, maxLogicalWidth);
 }
 
 bool RenderBlock::hasLineIfEmpty() const
 {
-    if (!node())
+    if (!element())
         return false;
     
-    if (node()->isRootEditableElement())
-        return true;
-    
-    if (node()->isShadowRoot() && isHTMLInputElement(toShadowRoot(node())->host()))
+    if (element()->isRootEditableElement())
         return true;
     
     return false;
@@ -6522,6 +2833,10 @@ bool RenderBlock::hasLineIfEmpty() const
 
 LayoutUnit RenderBlock::lineHeight(bool firstLine, LineDirectionMode direction, LinePositionMode linePositionMode) const
 {
+    // Anonymous inline blocks don't include margins or any real line height.
+    if (isAnonymousInlineBlock() && linePositionMode == PositionOnContainingLine)
+        return direction == HorizontalLine ? height() : width();
+    
     // Inline blocks are replaced elements. Otherwise, just pass off to
     // the base class.  If we're being queried as though we're the root line
     // box, then the fact that we're an inline-block is irrelevant, and we behave
@@ -6529,16 +2844,13 @@ LayoutUnit RenderBlock::lineHeight(bool firstLine, LineDirectionMode direction,
     if (isReplaced() && linePositionMode == PositionOnContainingLine)
         return RenderBox::lineHeight(firstLine, direction, linePositionMode);
 
-    if (firstLine && document()->styleSheetCollection()->usesFirstLineRules()) {
-        RenderStyle* s = style(firstLine);
-        if (s != style())
-            return s->computedLineHeight(view());
+    if (firstLine && view().usesFirstLineRules()) {
+        RenderStyle& s = firstLine ? firstLineStyle() : style();
+        if (&s != &style())
+            return s.computedLineHeight();
     }
     
-    if (m_lineHeight == -1)
-        m_lineHeight = style()->computedLineHeight(view());
-
-    return m_lineHeight;
+    return style().computedLineHeight();
 }
 
 int RenderBlock::baselinePosition(FontBaseline baselineType, bool firstLine, LineDirectionMode direction, LinePositionMode linePositionMode) const
@@ -6548,1227 +2860,635 @@ int RenderBlock::baselinePosition(FontBaseline baselineType, bool firstLine, Lin
     // box, then the fact that we're an inline-block is irrelevant, and we behave
     // just like a block.
     if (isReplaced() && linePositionMode == PositionOnContainingLine) {
+        if (isAnonymousInlineBlock())
+            return direction == HorizontalLine ? height() : width();
+        
         // For "leaf" theme objects, let the theme decide what the baseline position is.
         // FIXME: Might be better to have a custom CSS property instead, so that if the theme
         // is turned off, checkboxes/radios will still have decent baselines.
         // FIXME: Need to patch form controls to deal with vertical lines.
-        if (style()->hasAppearance() && !theme()->isControlContainer(style()->appearance()))
-            return theme()->baselinePosition(this);
+        if (style().hasAppearance() && !theme().isControlContainer(style().appearance()))
+            return theme().baselinePosition(*this);
             
         // CSS2.1 states that the baseline of an inline block is the baseline of the last line box in
         // the normal flow.  We make an exception for marquees, since their baselines are meaningless
         // (the content inside them moves).  This matches WinIE as well, which just bottom-aligns them.
         // We also give up on finding a baseline if we have a vertical scrollbar, or if we are scrolled
-        // vertically (e.g., an overflow:hidden block that has had scrollTop moved) or if the baseline is outside
-        // of our content box.
-        bool ignoreBaseline = (layer() && (layer()->marquee() || (direction == HorizontalLine ? (layer()->verticalScrollbar() || layer()->scrollYOffset() != 0)
-            : (layer()->horizontalScrollbar() || layer()->scrollXOffset() != 0)))) || (isWritingModeRoot() && !isRubyRun());
-        
-        int baselinePos = ignoreBaseline ? -1 : inlineBlockBaseline(direction);
-        
-        LayoutUnit bottomOfContent = direction == HorizontalLine ? borderTop() + paddingTop() + contentHeight() : borderRight() + paddingRight() + contentWidth();
-        if (baselinePos != -1 && baselinePos <= bottomOfContent)
-            return direction == HorizontalLine ? marginTop() + baselinePos : marginRight() + baselinePos;
-            
-        return RenderBox::baselinePosition(baselineType, firstLine, direction, linePositionMode);
-    }
-
-    const FontMetrics& fontMetrics = style(firstLine)->fontMetrics();
-    return fontMetrics.ascent(baselineType) + (lineHeight(firstLine, direction, linePositionMode) - fontMetrics.height()) / 2;
-}
-
-int RenderBlock::firstLineBoxBaseline() const
-{
-    if (!isBlockFlow() || (isWritingModeRoot() && !isRubyRun()))
-        return -1;
-
-    if (childrenInline()) {
-        if (firstLineBox())
-            return firstLineBox()->logicalTop() + style(true)->fontMetrics().ascent(firstRootBox()->baselineType());
-        else
-            return -1;
-    }
-    else {
-        for (RenderBox* curr = firstChildBox(); curr; curr = curr->nextSiblingBox()) {
-            if (!curr->isFloatingOrOutOfFlowPositioned()) {
-                int result = curr->firstLineBoxBaseline();
-                if (result != -1)
-                    return curr->logicalTop() + result; // Translate to our coordinate space.
-            }
-        }
-    }
-
-    return -1;
-}
-
-int RenderBlock::inlineBlockBaseline(LineDirectionMode direction) const
-{
-    return lastLineBoxBaseline(direction);
-}
-
-int RenderBlock::lastLineBoxBaseline(LineDirectionMode lineDirection) const
-{
-    if (!isBlockFlow() || (isWritingModeRoot() && !isRubyRun()))
-        return -1;
-
-    if (childrenInline()) {
-        if (!firstLineBox() && hasLineIfEmpty()) {
-            const FontMetrics& fontMetrics = firstLineStyle()->fontMetrics();
-            return fontMetrics.ascent()
-                 + (lineHeight(true, lineDirection, PositionOfInteriorLineBoxes) - fontMetrics.height()) / 2
-                 + (lineDirection == HorizontalLine ? borderTop() + paddingTop() : borderRight() + paddingRight());
-        }
-        if (lastLineBox())
-            return lastLineBox()->logicalTop() + style(lastLineBox() == firstLineBox())->fontMetrics().ascent(lastRootBox()->baselineType());
-        return -1;
-    } else {
-        bool haveNormalFlowChild = false;
-        for (RenderBox* curr = lastChildBox(); curr; curr = curr->previousSiblingBox()) {
-            if (!curr->isFloatingOrOutOfFlowPositioned()) {
-                haveNormalFlowChild = true;
-                int result = curr->inlineBlockBaseline(lineDirection);
-                if (result != -1)
-                    return curr->logicalTop() + result; // Translate to our coordinate space.
-            }
-        }
-        if (!haveNormalFlowChild && hasLineIfEmpty()) {
-            const FontMetrics& fontMetrics = firstLineStyle()->fontMetrics();
-            return fontMetrics.ascent()
-                 + (lineHeight(true, lineDirection, PositionOfInteriorLineBoxes) - fontMetrics.height()) / 2
-                 + (lineDirection == HorizontalLine ? borderTop() + paddingTop() : borderRight() + paddingRight());
-        }
-    }
-
-    return -1;
-}
-
-bool RenderBlock::containsNonZeroBidiLevel() const
-{
-    for (RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox()) {
-        for (InlineBox* box = root->firstLeafChild(); box; box = box->nextLeafChild()) {
-            if (box->bidiLevel())
-                return true;
-        }
-    }
-    return false;
-}
-
-RenderBlock* RenderBlock::firstLineBlock() const
-{
-    RenderBlock* firstLineBlock = const_cast<RenderBlock*>(this);
-    bool hasPseudo = false;
-    while (true) {
-        hasPseudo = firstLineBlock->style()->hasPseudoStyle(FIRST_LINE);
-        if (hasPseudo)
-            break;
-        RenderObject* parentBlock = firstLineBlock->parent();
-        // We include isRenderButton in this check because buttons are
-        // implemented using flex box but should still support first-line. The
-        // flex box spec requires that flex box does not support first-line,
-        // though.
-        // FIXME: Remove when buttons are implemented with align-items instead
-        // of flexbox.
-        if (firstLineBlock->isReplaced() || firstLineBlock->isFloating()
-            || !parentBlock || parentBlock->firstChild() != firstLineBlock || !parentBlock->isBlockFlow()
-            || (parentBlock->isFlexibleBox() && !parentBlock->isRenderButton()))
-            break;
-        ASSERT_WITH_SECURITY_IMPLICATION(parentBlock->isRenderBlock());
-        firstLineBlock = toRenderBlock(parentBlock);
-    } 
-    
-    if (!hasPseudo)
-        return 0;
-    
-    return firstLineBlock;
-}
-
-static RenderStyle* styleForFirstLetter(RenderObject* firstLetterBlock, RenderObject* firstLetterContainer)
-{
-    RenderStyle* pseudoStyle = firstLetterBlock->getCachedPseudoStyle(FIRST_LETTER, firstLetterContainer->firstLineStyle());
-    // Force inline display (except for floating first-letters).
-    pseudoStyle->setDisplay(pseudoStyle->isFloating() ? BLOCK : INLINE);
-    // CSS2 says first-letter can't be positioned.
-    pseudoStyle->setPosition(StaticPosition);
-    return pseudoStyle;
-}
-
-// CSS 2.1 http://www.w3.org/TR/CSS21/selector.html#first-letter
-// "Punctuation (i.e, characters defined in Unicode [UNICODE] in the "open" (Ps), "close" (Pe),
-// "initial" (Pi). "final" (Pf) and "other" (Po) punctuation classes), that precedes or follows the first letter should be included"
-static inline bool isPunctuationForFirstLetter(UChar c)
-{
-    CharCategory charCategory = category(c);
-    return charCategory == Punctuation_Open
-        || charCategory == Punctuation_Close
-        || charCategory == Punctuation_InitialQuote
-        || charCategory == Punctuation_FinalQuote
-        || charCategory == Punctuation_Other;
-}
-
-static inline bool shouldSkipForFirstLetter(UChar c)
-{
-    return isSpaceOrNewline(c) || c == noBreakSpace || isPunctuationForFirstLetter(c);
-}
-
-static inline RenderObject* findFirstLetterBlock(RenderBlock* start)
-{
-    RenderObject* firstLetterBlock = start;
-    while (true) {
-        // We include isRenderButton in these two checks because buttons are
-        // implemented using flex box but should still support first-letter.
-        // The flex box spec requires that flex box does not support
-        // first-letter, though.
-        // FIXME: Remove when buttons are implemented with align-items instead
-        // of flexbox.
-        bool canHaveFirstLetterRenderer = firstLetterBlock->style()->hasPseudoStyle(FIRST_LETTER)
-            && firstLetterBlock->canHaveGeneratedChildren()
-            && (!firstLetterBlock->isFlexibleBox() || firstLetterBlock->isRenderButton());
-        if (canHaveFirstLetterRenderer)
-            return firstLetterBlock;
-
-        RenderObject* parentBlock = firstLetterBlock->parent();
-        if (firstLetterBlock->isReplaced() || !parentBlock || parentBlock->firstChild() != firstLetterBlock || 
-            !parentBlock->isBlockFlow() || (parentBlock->isFlexibleBox() && !parentBlock->isRenderButton()))
-            return 0;
-        firstLetterBlock = parentBlock;
-    } 
-
-    return 0;
-}
-
-void RenderBlock::updateFirstLetterStyle(RenderObject* firstLetterBlock, RenderObject* currentChild)
-{
-    RenderObject* firstLetter = currentChild->parent();
-    RenderObject* firstLetterContainer = firstLetter->parent();
-    RenderStyle* pseudoStyle = styleForFirstLetter(firstLetterBlock, firstLetterContainer);
-    ASSERT(firstLetter->isFloating() || firstLetter->isInline());
-
-    if (Node::diff(firstLetter->style(), pseudoStyle, document()) == Node::Detach) {
-        // The first-letter renderer needs to be replaced. Create a new renderer of the right type.
-        RenderObject* newFirstLetter;
-        if (pseudoStyle->display() == INLINE)
-            newFirstLetter = RenderInline::createAnonymous(document());
-        else
-            newFirstLetter = RenderBlock::createAnonymous(document());
-        newFirstLetter->setStyle(pseudoStyle);
-
-        // Move the first letter into the new renderer.
-        LayoutStateDisabler layoutStateDisabler(view());
-        while (RenderObject* child = firstLetter->firstChild()) {
-            if (child->isText())
-                toRenderText(child)->removeAndDestroyTextBoxes();
-            firstLetter->removeChild(child);
-            newFirstLetter->addChild(child, 0);
-        }
-
-        RenderTextFragment* remainingText = 0;
-        RenderObject* nextSibling = firstLetter->nextSibling();
-        RenderObject* remainingTextObject = toRenderBoxModelObject(firstLetter)->firstLetterRemainingText();
-        if (remainingTextObject && remainingTextObject->isText() && toRenderText(remainingTextObject)->isTextFragment())
-            remainingText = toRenderTextFragment(remainingTextObject);
-        if (remainingText) {
-            ASSERT(remainingText->isAnonymous() || remainingText->node()->renderer() == remainingText);
-            // Replace the old renderer with the new one.
-            remainingText->setFirstLetter(newFirstLetter);
-            toRenderBoxModelObject(newFirstLetter)->setFirstLetterRemainingText(remainingText);
-        }
-        // To prevent removal of single anonymous block in RenderBlock::removeChild and causing
-        // |nextSibling| to go stale, we remove the old first letter using removeChildNode first.
-        firstLetterContainer->virtualChildren()->removeChildNode(firstLetterContainer, firstLetter);
-        firstLetter->destroy();
-        firstLetter = newFirstLetter;
-        firstLetterContainer->addChild(firstLetter, nextSibling);
-    } else
-        firstLetter->setStyle(pseudoStyle);
-
-    for (RenderObject* genChild = firstLetter->firstChild(); genChild; genChild = genChild->nextSibling()) {
-        if (genChild->isText())
-            genChild->setStyle(pseudoStyle);
-    }
-}
-
-void RenderBlock::createFirstLetterRenderer(RenderObject* firstLetterBlock, RenderObject* currentChild)
-{
-    RenderObject* firstLetterContainer = currentChild->parent();
-    RenderStyle* pseudoStyle = styleForFirstLetter(firstLetterBlock, firstLetterContainer);
-    RenderObject* firstLetter = 0;
-    if (pseudoStyle->display() == INLINE)
-        firstLetter = RenderInline::createAnonymous(document());
-    else
-        firstLetter = RenderBlock::createAnonymous(document());
-    firstLetter->setStyle(pseudoStyle);
-    firstLetterContainer->addChild(firstLetter, currentChild);
-
-    RenderText* textObj = toRenderText(currentChild);
-
-    // The original string is going to be either a generated content string or a DOM node's
-    // string.  We want the original string before it got transformed in case first-letter has
-    // no text-transform or a different text-transform applied to it.
-    RefPtr<StringImpl> oldText = textObj->originalText();
-    ASSERT(oldText);
-
-    if (oldText && oldText->length() > 0) {
-        unsigned length = 0;
-
-        // Account for leading spaces and punctuation.
-        while (length < oldText->length() && shouldSkipForFirstLetter((*oldText)[length]))
-            length++;
-
-        // Account for first letter.
-        length++;
-        
-        // Keep looking for whitespace and allowed punctuation, but avoid
-        // accumulating just whitespace into the :first-letter.
-        for (unsigned scanLength = length; scanLength < oldText->length(); ++scanLength) {
-            UChar c = (*oldText)[scanLength]; 
-            
-            if (!shouldSkipForFirstLetter(c))
-                break;
-
-            if (isPunctuationForFirstLetter(c))
-                length = scanLength + 1;
-         }
-         
-        // Construct a text fragment for the text after the first letter.
-        // This text fragment might be empty.
-        RenderTextFragment* remainingText = 
-            new (renderArena()) RenderTextFragment(textObj->node() ? textObj->node() : textObj->document(), oldText.get(), length, oldText->length() - length);
-        remainingText->setStyle(textObj->style());
-        if (remainingText->node())
-            remainingText->node()->setRenderer(remainingText);
-
-        firstLetterContainer->addChild(remainingText, textObj);
-        firstLetterContainer->removeChild(textObj);
-        remainingText->setFirstLetter(firstLetter);
-        toRenderBoxModelObject(firstLetter)->setFirstLetterRemainingText(remainingText);
+        // vertically (e.g., an overflow:hidden block that has had scrollTop moved).
+        bool ignoreBaseline = (layer() && (layer()->marquee() || (direction == HorizontalLine ? (layer()->verticalScrollbar() || layer()->scrollOffset().y() != 0)
+            : (layer()->horizontalScrollbar() || layer()->scrollOffset().x() != 0)))) || (isWritingModeRoot() && !isRubyRun());
         
-        // construct text fragment for the first letter
-        RenderTextFragment* letter = 
-            new (renderArena()) RenderTextFragment(remainingText->node() ? remainingText->node() : remainingText->document(), oldText.get(), 0, length);
-        letter->setStyle(pseudoStyle);
-        firstLetter->addChild(letter);
-
-        textObj->destroy();
-    }
-}
-
-void RenderBlock::updateFirstLetter()
-{
-    if (!document()->styleSheetCollection()->usesFirstLetterRules())
-        return;
-    // Don't recur
-    if (style()->styleType() == FIRST_LETTER)
-        return;
-
-    // FIXME: We need to destroy the first-letter object if it is no longer the first child. Need to find
-    // an efficient way to check for that situation though before implementing anything.
-    RenderObject* firstLetterBlock = findFirstLetterBlock(this);
-    if (!firstLetterBlock)
-        return;
-
-    // Drill into inlines looking for our first text child.
-    RenderObject* currChild = firstLetterBlock->firstChild();
-    while (currChild) {
-        if (currChild->isText())
-            break;
-        if (currChild->isListMarker())
-            currChild = currChild->nextSibling();
-        else if (currChild->isFloatingOrOutOfFlowPositioned()) {
-            if (currChild->style()->styleType() == FIRST_LETTER) {
-                currChild = currChild->firstChild();
-                break;
-            }
-            currChild = currChild->nextSibling();
-        } else if (currChild->isReplaced() || currChild->isRenderButton() || currChild->isMenuList())
-            break;
-        else if (currChild->style()->hasPseudoStyle(FIRST_LETTER) && currChild->canHaveGeneratedChildren())  {
-            // We found a lower-level node with first-letter, which supersedes the higher-level style
-            firstLetterBlock = currChild;
-            currChild = currChild->firstChild();
-        } else
-            currChild = currChild->firstChild();
-    }
-
-    if (!currChild)
-        return;
-
-    // If the child already has style, then it has already been created, so we just want
-    // to update it.
-    if (currChild->parent()->style()->styleType() == FIRST_LETTER) {
-        updateFirstLetterStyle(firstLetterBlock, currChild);
-        return;
-    }
-
-    if (!currChild->isText() || currChild->isBR())
-        return;
-
-    // Our layout state is not valid for the repaints we are going to trigger by
-    // adding and removing children of firstLetterContainer.
-    LayoutStateDisabler layoutStateDisabler(view());
-
-    createFirstLetterRenderer(firstLetterBlock, currChild);
-}
-
-// Helper methods for obtaining the last line, computing line counts and heights for line counts
-// (crawling into blocks).
-static bool shouldCheckLines(RenderObject* obj)
-{
-    return !obj->isFloatingOrOutOfFlowPositioned() && !obj->isRunIn()
-            && obj->isBlockFlow() && obj->style()->height().isAuto()
-            && (!obj->isDeprecatedFlexibleBox() || obj->style()->boxOrient() == VERTICAL);
-}
-
-static int getHeightForLineCount(RenderBlock* block, int l, bool includeBottom, int& count)
-{
-    if (block->style()->visibility() == VISIBLE) {
-        if (block->childrenInline()) {
-            for (RootInlineBox* box = block->firstRootBox(); box; box = box->nextRootBox()) {
-                if (++count == l)
-                    return box->lineBottom() + (includeBottom ? (block->borderBottom() + block->paddingBottom()) : LayoutUnit());
-            }
-        }
-        else {
-            RenderBox* normalFlowChildWithoutLines = 0;
-            for (RenderBox* obj = block->firstChildBox(); obj; obj = obj->nextSiblingBox()) {
-                if (shouldCheckLines(obj)) {
-                    int result = getHeightForLineCount(toRenderBlock(obj), l, false, count);
-                    if (result != -1)
-                        return result + obj->y() + (includeBottom ? (block->borderBottom() + block->paddingBottom()) : LayoutUnit());
-                } else if (!obj->isFloatingOrOutOfFlowPositioned() && !obj->isRunIn())
-                    normalFlowChildWithoutLines = obj;
-            }
-            if (normalFlowChildWithoutLines && l == 0)
-                return normalFlowChildWithoutLines->y() + normalFlowChildWithoutLines->height();
-        }
-    }
-    
-    return -1;
-}
-
-RootInlineBox* RenderBlock::lineAtIndex(int i) const
-{
-    ASSERT(i >= 0);
-
-    if (style()->visibility() != VISIBLE)
-        return 0;
-
-    if (childrenInline()) {
-        for (RootInlineBox* box = firstRootBox(); box; box = box->nextRootBox())
-            if (!i--)
-                return box;
-    } else {
-        for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
-            if (!shouldCheckLines(child))
-                continue;
-            if (RootInlineBox* box = toRenderBlock(child)->lineAtIndex(i))
-                return box;
-        }
-    }
-
-    return 0;
-}
-
-int RenderBlock::lineCount(const RootInlineBox* stopRootInlineBox, bool* found) const
-{
-    int count = 0;
-
-    if (style()->visibility() == VISIBLE) {
-        if (childrenInline())
-            for (RootInlineBox* box = firstRootBox(); box; box = box->nextRootBox()) {
-                count++;
-                if (box == stopRootInlineBox) {
-                    if (found)
-                        *found = true;
-                    break;
-                }
-            }
-        else
-            for (RenderObject* obj = firstChild(); obj; obj = obj->nextSibling())
-                if (shouldCheckLines(obj)) {
-                    bool recursiveFound = false;
-                    count += toRenderBlock(obj)->lineCount(stopRootInlineBox, &recursiveFound);
-                    if (recursiveFound) {
-                        if (found)
-                            *found = true;
-                        break;
-                    }
-                }
-    }
-    return count;
-}
-
-int RenderBlock::heightForLineCount(int l)
-{
-    int count = 0;
-    return getHeightForLineCount(this, l, true, count);
-}
-
-void RenderBlock::adjustForBorderFit(LayoutUnit x, LayoutUnit& left, LayoutUnit& right) const
-{
-    // We don't deal with relative positioning.  Our assumption is that you shrink to fit the lines without accounting
-    // for either overflow or translations via relative positioning.
-    if (style()->visibility() == VISIBLE) {
-        if (childrenInline()) {
-            for (RootInlineBox* box = firstRootBox(); box; box = box->nextRootBox()) {
-                if (box->firstChild())
-                    left = min(left, x + static_cast<LayoutUnit>(box->firstChild()->x()));
-                if (box->lastChild())
-                    right = max(right, x + static_cast<LayoutUnit>(ceilf(box->lastChild()->logicalRight())));
-            }
-        }
-        else {
-            for (RenderBox* obj = firstChildBox(); obj; obj = obj->nextSiblingBox()) {
-                if (!obj->isFloatingOrOutOfFlowPositioned()) {
-                    if (obj->isBlockFlow() && !obj->hasOverflowClip())
-                        toRenderBlock(obj)->adjustForBorderFit(x + obj->x(), left, right);
-                    else if (obj->style()->visibility() == VISIBLE) {
-                        // We are a replaced element or some kind of non-block-flow object.
-                        left = min(left, x + obj->x());
-                        right = max(right, x + obj->x() + obj->width());
-                    }
-                }
-            }
-        }
+        Optional<int> baselinePos = ignoreBaseline ? Optional<int>() : inlineBlockBaseline(direction);
         
-        if (m_floatingObjects) {
-            const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
-            FloatingObjectSetIterator end = floatingObjectSet.end();
-            for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
-                FloatingObject* r = *it;
-                // Only examine the object if our m_shouldPaint flag is set.
-                if (r->shouldPaint()) {
-                    LayoutUnit floatLeft = xPositionForFloatIncludingMargin(r) - r->m_renderer->x();
-                    LayoutUnit floatRight = floatLeft + r->m_renderer->width();
-                    left = min(left, floatLeft);
-                    right = max(right, floatRight);
-                }
-            }
-        }
-    }
-}
-
-void RenderBlock::fitBorderToLinesIfNeeded()
-{
-    if (style()->borderFit() == BorderFitBorder || hasOverrideWidth())
-        return;
-
-    // Walk any normal flow lines to snugly fit.
-    LayoutUnit left = LayoutUnit::max();
-    LayoutUnit right = LayoutUnit::min();
-    LayoutUnit oldWidth = contentWidth();
-    adjustForBorderFit(0, left, right);
-    
-    // Clamp to our existing edges. We can never grow. We only shrink.
-    LayoutUnit leftEdge = borderLeft() + paddingLeft();
-    LayoutUnit rightEdge = leftEdge + oldWidth;
-    left = min(rightEdge, max(leftEdge, left));
-    right = max(leftEdge, min(rightEdge, right));
-    
-    LayoutUnit newContentWidth = right - left;
-    if (newContentWidth == oldWidth)
-        return;
-    
-    setOverrideLogicalContentWidth(newContentWidth);
-    layoutBlock(false);
-    clearOverrideLogicalContentWidth();
-}
-
-void RenderBlock::clearTruncation()
-{
-    if (style()->visibility() == VISIBLE) {
-        if (childrenInline() && hasMarkupTruncation()) {
-            setHasMarkupTruncation(false);
-            for (RootInlineBox* box = firstRootBox(); box; box = box->nextRootBox())
-                box->clearTruncation();
-        } else {
-            for (RenderObject* obj = firstChild(); obj; obj = obj->nextSibling()) {
-                if (shouldCheckLines(obj))
-                    toRenderBlock(obj)->clearTruncation();
-            }
-        }
-    }
-}
-
-void RenderBlock::setMaxMarginBeforeValues(LayoutUnit pos, LayoutUnit neg)
-{
-    if (!m_rareData) {
-        if (pos == RenderBlockRareData::positiveMarginBeforeDefault(this) && neg == RenderBlockRareData::negativeMarginBeforeDefault(this))
-            return;
-        m_rareData = adoptPtr(new RenderBlockRareData(this));
+        if (isDeprecatedFlexibleBox()) {
+            // Historically, we did this check for all baselines. But we can't
+            // remove this code from deprecated flexbox, because it effectively
+            // breaks -webkit-line-clamp, which is used in the wild -- we would
+            // calculate the baseline as if -webkit-line-clamp wasn't used.
+            // For simplicity, we use this for all uses of deprecated flexbox.
+            LayoutUnit bottomOfContent = direction == HorizontalLine ? borderTop() + paddingTop() + contentHeight() : borderRight() + paddingRight() + contentWidth();
+            if (baselinePos && baselinePos.value() > bottomOfContent)
+                baselinePos = Optional<int>();
+        }
+        if (baselinePos)
+            return direction == HorizontalLine ? marginTop() + baselinePos.value() : marginRight() + baselinePos.value();
+
+        return RenderBox::baselinePosition(baselineType, firstLine, direction, linePositionMode);
     }
-    m_rareData->m_margins.setPositiveMarginBefore(pos);
-    m_rareData->m_margins.setNegativeMarginBefore(neg);
+
+    const RenderStyle& style = firstLine ? firstLineStyle() : this->style();
+    const FontMetrics& fontMetrics = style.fontMetrics();
+    return fontMetrics.ascent(baselineType) + (lineHeight(firstLine, direction, linePositionMode) - fontMetrics.height()) / 2;
 }
 
-void RenderBlock::setMaxMarginAfterValues(LayoutUnit pos, LayoutUnit neg)
+LayoutUnit RenderBlock::minLineHeightForReplacedRenderer(bool isFirstLine, LayoutUnit replacedHeight) const
 {
-    if (!m_rareData) {
-        if (pos == RenderBlockRareData::positiveMarginAfterDefault(this) && neg == RenderBlockRareData::negativeMarginAfterDefault(this))
-            return;
-        m_rareData = adoptPtr(new RenderBlockRareData(this));
-    }
-    m_rareData->m_margins.setPositiveMarginAfter(pos);
-    m_rareData->m_margins.setNegativeMarginAfter(neg);
+    if (!document().inNoQuirksMode() && replacedHeight)
+        return replacedHeight;
+
+    const RenderStyle& style = isFirstLine ? firstLineStyle() : this->style();
+    if (!(style.lineBoxContain() & LineBoxContainBlock))
+        return 0;
+
+    return std::max<LayoutUnit>(replacedHeight, lineHeight(isFirstLine, isHorizontalWritingMode() ? HorizontalLine : VerticalLine, PositionOfInteriorLineBoxes));
 }
 
-void RenderBlock::setMustDiscardMarginBefore(bool value)
+Optional<int> RenderBlock::firstLineBaseline() const
 {
-    if (style()->marginBeforeCollapse() == MDISCARD) {
-        ASSERT(value);
-        return;
-    }
-    
-    if (!m_rareData && !value)
-        return;
+    if (isWritingModeRoot() && !isRubyRun())
+        return Optional<int>();
 
-    if (!m_rareData)
-        m_rareData = adoptPtr(new RenderBlockRareData(this));
+    for (RenderBox* curr = firstChildBox(); curr; curr = curr->nextSiblingBox()) {
+        if (!curr->isFloatingOrOutOfFlowPositioned()) {
+            if (Optional<int> result = curr->firstLineBaseline())
+                return Optional<int>(curr->logicalTop() + result.value()); // Translate to our coordinate space.
+        }
+    }
 
-    m_rareData->m_discardMarginBefore = value;
+    return Optional<int>();
 }
 
-void RenderBlock::setMustDiscardMarginAfter(bool value)
+Optional<int> RenderBlock::inlineBlockBaseline(LineDirectionMode lineDirection) const
 {
-    if (style()->marginAfterCollapse() == MDISCARD) {
-        ASSERT(value);
-        return;
-    }
+    if (isWritingModeRoot() && !isRubyRun())
+        return Optional<int>();
 
-    if (!m_rareData && !value)
-        return;
+    bool haveNormalFlowChild = false;
+    for (auto* box = lastChildBox(); box; box = box->previousSiblingBox()) {
+        if (box->isFloatingOrOutOfFlowPositioned())
+            continue;
+        haveNormalFlowChild = true;
+        if (Optional<int> result = box->inlineBlockBaseline(lineDirection))
+            return Optional<int>(box->logicalTop() + result.value()); // Translate to our coordinate space.
+    }
 
-    if (!m_rareData)
-        m_rareData = adoptPtr(new RenderBlockRareData(this));
+    if (!haveNormalFlowChild && hasLineIfEmpty()) {
+        auto& fontMetrics = firstLineStyle().fontMetrics();
+        return Optional<int>(fontMetrics.ascent()
+            + (lineHeight(true, lineDirection, PositionOfInteriorLineBoxes) - fontMetrics.height()) / 2
+            + (lineDirection == HorizontalLine ? borderTop() + paddingTop() : borderRight() + paddingRight()));
+    }
 
-    m_rareData->m_discardMarginAfter = value;
+    return Optional<int>();
 }
 
-bool RenderBlock::mustDiscardMarginBefore() const
+static inline bool isRenderBlockFlowOrRenderButton(RenderElement& renderElement)
 {
-    return style()->marginBeforeCollapse() == MDISCARD || (m_rareData && m_rareData->m_discardMarginBefore);
+    // We include isRenderButton in this check because buttons are implemented
+    // using flex box but should still support first-line|first-letter.
+    // The flex box and specs require that flex box and grid do not support
+    // first-line|first-letter, though.
+    // FIXME: Remove when buttons are implemented with align-items instead of
+    // flex box.
+    return renderElement.isRenderBlockFlow() || renderElement.isRenderButton();
 }
 
-bool RenderBlock::mustDiscardMarginAfter() const
+RenderBlock* RenderBlock::firstLineBlock() const
 {
-    return style()->marginAfterCollapse() == MDISCARD || (m_rareData && m_rareData->m_discardMarginAfter);
+    RenderBlock* firstLineBlock = const_cast<RenderBlock*>(this);
+    bool hasPseudo = false;
+    while (true) {
+        hasPseudo = firstLineBlock->style().hasPseudoStyle(FIRST_LINE);
+        if (hasPseudo)
+            break;
+        RenderElement* parentBlock = firstLineBlock->parent();
+        if (firstLineBlock->isReplaced() || firstLineBlock->isFloating()
+            || !parentBlock || parentBlock->firstChild() != firstLineBlock || !isRenderBlockFlowOrRenderButton(*parentBlock))
+            break;
+        firstLineBlock = downcast<RenderBlock>(parentBlock);
+    } 
+    
+    if (!hasPseudo)
+        return nullptr;
+    
+    return firstLineBlock;
 }
 
-bool RenderBlock::mustDiscardMarginBeforeForChild(const RenderBox* child) const
+static RenderStyle& styleForFirstLetter(RenderElement* firstLetterBlock, RenderObject* firstLetterContainer)
 {
-    ASSERT(!child->selfNeedsLayout());
-    if (!child->isWritingModeRoot())
-        return child->isRenderBlock() ? toRenderBlock(child)->mustDiscardMarginBefore() : (child->style()->marginBeforeCollapse() == MDISCARD);
-    if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
-        return child->isRenderBlock() ? toRenderBlock(child)->mustDiscardMarginAfter() : (child->style()->marginAfterCollapse() == MDISCARD);
+    RenderStyle* pseudoStyle = firstLetterBlock->getCachedPseudoStyle(FIRST_LETTER, &firstLetterContainer->firstLineStyle());
+    
+    // If we have an initial letter drop that is >= 1, then we need to force floating to be on.
+    if (pseudoStyle->initialLetterDrop() >= 1 && !pseudoStyle->isFloating())
+        pseudoStyle->setFloating(pseudoStyle->isLeftToRightDirection() ? LeftFloat : RightFloat);
 
-    // FIXME: We return false here because the implementation is not geometrically complete. We have values only for before/after, not start/end.
-    // In case the boxes are perpendicular we assume the property is not specified.
-    return false;
+    // We have to compute the correct font-size for the first-letter if it has an initial letter height set.
+    RenderObject* paragraph = firstLetterContainer->isRenderBlockFlow() ? firstLetterContainer : firstLetterContainer->containingBlock();
+    if (pseudoStyle->initialLetterHeight() >= 1 && pseudoStyle->fontMetrics().hasCapHeight() && paragraph->style().fontMetrics().hasCapHeight()) {
+        // FIXME: For ideographic baselines, we want to go from line edge to line edge. This is equivalent to (N-1)*line-height + the font height.
+        // We don't yet support ideographic baselines.
+        // For an N-line first-letter and for alphabetic baselines, the cap-height of the first letter needs to equal (N-1)*line-height of paragraph lines + cap-height of the paragraph
+        // Mathematically we can't rely on font-size, since font().height() doesn't necessarily match. For reliability, the best approach is simply to
+        // compare the final measured cap-heights of the two fonts in order to get to the closest possible value.
+        pseudoStyle->setLineBoxContain(LineBoxContainInitialLetter);
+        int lineHeight = paragraph->style().computedLineHeight();
+        
+        // Set the font to be one line too big and then ratchet back to get to a precise fit. We can't just set the desired font size based off font height metrics
+        // because many fonts bake ascent into the font metrics. Therefore we have to look at actual measured cap height values in order to know when we have a good fit.
+        auto newFontDescription = pseudoStyle->fontDescription();
+        float capRatio = pseudoStyle->fontMetrics().floatCapHeight() / pseudoStyle->fontSize();
+        float startingFontSize = ((pseudoStyle->initialLetterHeight() - 1) * lineHeight + paragraph->style().fontMetrics().capHeight()) / capRatio;
+        newFontDescription.setSpecifiedSize(startingFontSize);
+        newFontDescription.setComputedSize(startingFontSize);
+        pseudoStyle->setFontDescription(newFontDescription);
+        pseudoStyle->fontCascade().update(pseudoStyle->fontCascade().fontSelector());
+        
+        int desiredCapHeight = (pseudoStyle->initialLetterHeight() - 1) * lineHeight + paragraph->style().fontMetrics().capHeight();
+        int actualCapHeight = pseudoStyle->fontMetrics().capHeight();
+        while (actualCapHeight > desiredCapHeight) {
+            auto newFontDescription = pseudoStyle->fontDescription();
+            newFontDescription.setSpecifiedSize(newFontDescription.specifiedSize() - 1);
+            newFontDescription.setComputedSize(newFontDescription.computedSize() -1);
+            pseudoStyle->setFontDescription(newFontDescription);
+            pseudoStyle->fontCascade().update(pseudoStyle->fontCascade().fontSelector());
+            actualCapHeight = pseudoStyle->fontMetrics().capHeight();
+        }
+    }
+    
+    // Force inline display (except for floating first-letters).
+    pseudoStyle->setDisplay(pseudoStyle->isFloating() ? BLOCK : INLINE);
+    // CSS2 says first-letter can't be positioned.
+    pseudoStyle->setPosition(StaticPosition);
+    return *pseudoStyle;
 }
 
-bool RenderBlock::mustDiscardMarginAfterForChild(const RenderBox* child) const
+// CSS 2.1 http://www.w3.org/TR/CSS21/selector.html#first-letter
+// "Punctuation (i.e, characters defined in Unicode [UNICODE] in the "open" (Ps), "close" (Pe),
+// "initial" (Pi). "final" (Pf) and "other" (Po) punctuation classes), that precedes or follows the first letter should be included"
+static inline bool isPunctuationForFirstLetter(UChar c)
 {
-    ASSERT(!child->selfNeedsLayout());
-    if (!child->isWritingModeRoot())
-        return child->isRenderBlock() ? toRenderBlock(child)->mustDiscardMarginAfter() : (child->style()->marginAfterCollapse() == MDISCARD);
-    if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
-        return child->isRenderBlock() ? toRenderBlock(child)->mustDiscardMarginBefore() : (child->style()->marginBeforeCollapse() == MDISCARD);
-
-    // FIXME: See |mustDiscardMarginBeforeForChild| above.
-    return false;
+    return U_GET_GC_MASK(c) & (U_GC_PS_MASK | U_GC_PE_MASK | U_GC_PI_MASK | U_GC_PF_MASK | U_GC_PO_MASK);
 }
 
-bool RenderBlock::mustSeparateMarginBeforeForChild(const RenderBox* child) const
+static inline bool shouldSkipForFirstLetter(UChar c)
 {
-    ASSERT(!child->selfNeedsLayout());
-    const RenderStyle* childStyle = child->style();
-    if (!child->isWritingModeRoot())
-        return childStyle->marginBeforeCollapse() == MSEPARATE;
-    if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
-        return childStyle->marginAfterCollapse() == MSEPARATE;
-
-    // FIXME: See |mustDiscardMarginBeforeForChild| above.
-    return false;
+    return isSpaceOrNewline(c) || c == noBreakSpace || isPunctuationForFirstLetter(c);
 }
 
-bool RenderBlock::mustSeparateMarginAfterForChild(const RenderBox* child) const
+static inline RenderBlock* findFirstLetterBlock(RenderBlock* start)
 {
-    ASSERT(!child->selfNeedsLayout());
-    const RenderStyle* childStyle = child->style();
-    if (!child->isWritingModeRoot())
-        return childStyle->marginAfterCollapse() == MSEPARATE;
-    if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
-        return childStyle->marginBeforeCollapse() == MSEPARATE;
+    RenderBlock* firstLetterBlock = start;
+    while (true) {
+        bool canHaveFirstLetterRenderer = firstLetterBlock->style().hasPseudoStyle(FIRST_LETTER)
+            && firstLetterBlock->canHaveGeneratedChildren()
+            && isRenderBlockFlowOrRenderButton(*firstLetterBlock);
+        if (canHaveFirstLetterRenderer)
+            return firstLetterBlock;
 
-    // FIXME: See |mustDiscardMarginBeforeForChild| above.
-    return false;
-}
+        RenderElement* parentBlock = firstLetterBlock->parent();
+        if (firstLetterBlock->isReplaced() || !parentBlock || parentBlock->firstChild() != firstLetterBlock
+            || !isRenderBlockFlowOrRenderButton(*parentBlock))
+            return nullptr;
+        firstLetterBlock = downcast<RenderBlock>(parentBlock);
+    } 
 
-void RenderBlock::setPaginationStrut(LayoutUnit strut)
-{
-    if (!m_rareData) {
-        if (!strut)
-            return;
-        m_rareData = adoptPtr(new RenderBlockRareData(this));
-    }
-    m_rareData->m_paginationStrut = strut;
+    return nullptr;
 }
 
-void RenderBlock::setPageLogicalOffset(LayoutUnit logicalOffset)
+void RenderBlock::updateFirstLetterStyle(RenderElement* firstLetterBlock, RenderObject* currentChild)
 {
-    if (!m_rareData) {
-        if (!logicalOffset)
-            return;
-        m_rareData = adoptPtr(new RenderBlockRareData(this));
-    }
-    m_rareData->m_pageLogicalOffset = logicalOffset;
-}
+    RenderElement* firstLetter = currentChild->parent();
+    RenderElement* firstLetterContainer = firstLetter->parent();
+    RenderStyle& pseudoStyle = styleForFirstLetter(firstLetterBlock, firstLetterContainer);
+    ASSERT(firstLetter->isFloating() || firstLetter->isInline());
 
-void RenderBlock::setBreakAtLineToAvoidWidow(RootInlineBox* lineToBreak)
-{
-    ASSERT(lineToBreak);
-    if (!m_rareData)
-        m_rareData = adoptPtr(new RenderBlockRareData(this));
-    m_rareData->m_shouldBreakAtLineToAvoidWidow = true;
-    m_rareData->m_lineBreakToAvoidWidow = lineToBreak;
-}
+    if (Style::determineChange(firstLetter->style(), pseudoStyle) == Style::Detach) {
+        // The first-letter renderer needs to be replaced. Create a new renderer of the right type.
+        RenderBoxModelObject* newFirstLetter;
+        if (pseudoStyle.display() == INLINE)
+            newFirstLetter = new RenderInline(document(), pseudoStyle);
+        else
+            newFirstLetter = new RenderBlockFlow(document(), pseudoStyle);
+        newFirstLetter->initializeStyle();
 
-void RenderBlock::clearShouldBreakAtLineToAvoidWidow() const
-{
-    if (!m_rareData)
-        return;
-    m_rareData->m_shouldBreakAtLineToAvoidWidow = false;
-    m_rareData->m_lineBreakToAvoidWidow = 0;
-}
+        // Move the first letter into the new renderer.
+        LayoutStateDisabler layoutStateDisabler(view());
+        while (RenderObject* child = firstLetter->firstChild()) {
+            if (is<RenderText>(*child))
+                downcast<RenderText>(*child).removeAndDestroyTextBoxes();
+            firstLetter->removeChild(*child);
+            newFirstLetter->addChild(child, nullptr);
+        }
 
-void RenderBlock::absoluteRects(Vector<IntRect>& rects, const LayoutPoint& accumulatedOffset) const
-{
-    // For blocks inside inlines, we go ahead and include margins so that we run right up to the
-    // inline boxes above and below us (thus getting merged with them to form a single irregular
-    // shape).
-    if (isAnonymousBlockContinuation()) {
-        // FIXME: This is wrong for block-flows that are horizontal.
-        // https://bugs.webkit.org/show_bug.cgi?id=46781
-        rects.append(pixelSnappedIntRect(accumulatedOffset.x(), accumulatedOffset.y() - collapsedMarginBefore(),
-                                width(), height() + collapsedMarginBefore() + collapsedMarginAfter()));
-        continuation()->absoluteRects(rects, accumulatedOffset - toLayoutSize(location() +
-                inlineElementContinuation()->containingBlock()->location()));
+        RenderObject* nextSibling = firstLetter->nextSibling();
+        if (RenderTextFragment* remainingText = downcast<RenderBoxModelObject>(*firstLetter).firstLetterRemainingText()) {
+            ASSERT(remainingText->isAnonymous() || remainingText->textNode()->renderer() == remainingText);
+            // Replace the old renderer with the new one.
+            remainingText->setFirstLetter(*newFirstLetter);
+            newFirstLetter->setFirstLetterRemainingText(remainingText);
+        }
+        // To prevent removal of single anonymous block in RenderBlock::removeChild and causing
+        // |nextSibling| to go stale, we remove the old first letter using removeChildNode first.
+        firstLetterContainer->removeChildInternal(*firstLetter, NotifyChildren);
+        firstLetter->destroy();
+        firstLetter = newFirstLetter;
+        firstLetterContainer->addChild(firstLetter, nextSibling);
     } else
-        rects.append(pixelSnappedIntRect(accumulatedOffset, size()));
+        firstLetter->setStyle(pseudoStyle);
 }
 
-void RenderBlock::absoluteQuads(Vector<FloatQuad>& quads, bool* wasFixed) const
+void RenderBlock::createFirstLetterRenderer(RenderElement* firstLetterBlock, RenderText* currentTextChild)
 {
-    // For blocks inside inlines, we go ahead and include margins so that we run right up to the
-    // inline boxes above and below us (thus getting merged with them to form a single irregular
-    // shape).
-    if (isAnonymousBlockContinuation()) {
-        // FIXME: This is wrong for block-flows that are horizontal.
-        // https://bugs.webkit.org/show_bug.cgi?id=46781
-        FloatRect localRect(0, -collapsedMarginBefore(),
-                            width(), height() + collapsedMarginBefore() + collapsedMarginAfter());
-        quads.append(localToAbsoluteQuad(localRect, 0 /* mode */, wasFixed));
-        continuation()->absoluteQuads(quads, wasFixed);
-    } else
-        quads.append(RenderBox::localToAbsoluteQuad(FloatRect(0, 0, width(), height()), 0 /* mode */, wasFixed));
-}
+    RenderElement* firstLetterContainer = currentTextChild->parent();
+    RenderStyle& pseudoStyle = styleForFirstLetter(firstLetterBlock, firstLetterContainer);
+    RenderBoxModelObject* firstLetter = nullptr;
+    if (pseudoStyle.display() == INLINE)
+        firstLetter = new RenderInline(document(), pseudoStyle);
+    else
+        firstLetter = new RenderBlockFlow(document(), pseudoStyle);
+    firstLetter->initializeStyle();
+    firstLetterContainer->addChild(firstLetter, currentTextChild);
 
-LayoutRect RenderBlock::rectWithOutlineForRepaint(const RenderLayerModelObject* repaintContainer, LayoutUnit outlineWidth) const
-{
-    LayoutRect r(RenderBox::rectWithOutlineForRepaint(repaintContainer, outlineWidth));
-    if (isAnonymousBlockContinuation())
-        r.inflateY(collapsedMarginBefore()); // FIXME: This is wrong for block-flows that are horizontal.
-    return r;
-}
+    // The original string is going to be either a generated content string or a DOM node's
+    // string.  We want the original string before it got transformed in case first-letter has
+    // no text-transform or a different text-transform applied to it.
+    String oldText = currentTextChild->originalText();
+    ASSERT(!oldText.isNull());
 
-RenderObject* RenderBlock::hoverAncestor() const
-{
-    return isAnonymousBlockContinuation() ? continuation() : RenderBox::hoverAncestor();
-}
+    if (!oldText.isEmpty()) {
+        unsigned length = 0;
 
-void RenderBlock::updateDragState(bool dragOn)
-{
-    RenderBox::updateDragState(dragOn);
-    if (continuation())
-        continuation()->updateDragState(dragOn);
-}
+        // Account for leading spaces and punctuation.
+        while (length < oldText.length() && shouldSkipForFirstLetter(oldText[length]))
+            length++;
 
-RenderStyle* RenderBlock::outlineStyleForRepaint() const
-{
-    return isAnonymousBlockContinuation() ? continuation()->style() : style();
-}
+        // Account for first grapheme cluster.
+        length += numCharactersInGraphemeClusters(StringView(oldText).substring(length), 1);
+        
+        // Keep looking for whitespace and allowed punctuation, but avoid
+        // accumulating just whitespace into the :first-letter.
+        for (unsigned scanLength = length; scanLength < oldText.length(); ++scanLength) {
+            UChar c = oldText[scanLength];
+            
+            if (!shouldSkipForFirstLetter(c))
+                break;
 
-void RenderBlock::childBecameNonInline(RenderObject*)
-{
-    makeChildrenNonInline();
-    if (isAnonymousBlock() && parent() && parent()->isRenderBlock())
-        toRenderBlock(parent())->removeLeftoverAnonymousBlock(this);
-    // |this| may be dead here
-}
+            if (isPunctuationForFirstLetter(c))
+                length = scanLength + 1;
+         }
+         
+        // Construct a text fragment for the text after the first letter.
+        // This text fragment might be empty.
+        RenderTextFragment* remainingText;
+        if (currentTextChild->textNode())
+            remainingText = new RenderTextFragment(*currentTextChild->textNode(), oldText, length, oldText.length() - length);
+        else
+            remainingText = new RenderTextFragment(document(), oldText, length, oldText.length() - length);
 
-void RenderBlock::updateHitTestResult(HitTestResult& result, const LayoutPoint& point)
-{
-    if (result.innerNode())
-        return;
+        if (remainingText->textNode())
+            remainingText->textNode()->setRenderer(remainingText);
 
-    if (Node* n = nodeForHitTest()) {
-        result.setInnerNode(n);
-        if (!result.innerNonSharedNode())
-            result.setInnerNonSharedNode(n);
-        result.setLocalPoint(point);
+        firstLetterContainer->addChild(remainingText, currentTextChild);
+        firstLetterContainer->removeChild(*currentTextChild);
+        remainingText->setFirstLetter(*firstLetter);
+        firstLetter->setFirstLetterRemainingText(remainingText);
+        
+        // construct text fragment for the first letter
+        RenderTextFragment* letter;
+        if (remainingText->textNode())
+            letter = new RenderTextFragment(*remainingText->textNode(), oldText, 0, length);
+        else
+            letter = new RenderTextFragment(document(), oldText, 0, length);
+
+        firstLetter->addChild(letter);
+
+        currentTextChild->destroy();
     }
 }
-
-LayoutRect RenderBlock::localCaretRect(InlineBox* inlineBox, int caretOffset, LayoutUnit* extraWidthToEndOfLine)
+    
+void RenderBlock::getFirstLetter(RenderObject*& firstLetter, RenderElement*& firstLetterContainer, RenderObject* skipObject)
 {
-    // Do the normal calculation in most cases.
-    if (firstChild())
-        return RenderBox::localCaretRect(inlineBox, caretOffset, extraWidthToEndOfLine);
+    firstLetter = nullptr;
+    firstLetterContainer = nullptr;
 
-    LayoutRect caretRect = localCaretRectForEmptyElement(width(), textIndentOffset());
+    if (!view().usesFirstLetterRules())
+        return;
 
-    // FIXME: Does this need to adjust for vertical orientation?
-    if (extraWidthToEndOfLine)
-        *extraWidthToEndOfLine = width() - caretRect.maxX();
+    // Don't recur
+    if (style().styleType() == FIRST_LETTER)
+        return;
+    
+    // FIXME: We need to destroy the first-letter object if it is no longer the first child. Need to find
+    // an efficient way to check for that situation though before implementing anything.
+    firstLetterContainer = findFirstLetterBlock(this);
+    if (!firstLetterContainer)
+        return;
+    
+    // Drill into inlines looking for our first text descendant.
+    firstLetter = firstLetterContainer->firstChild();
+    while (firstLetter) {
+        if (is<RenderText>(*firstLetter)) {
+            if (firstLetter == skipObject) {
+                firstLetter = firstLetter->nextSibling();
+                continue;
+            }
+            
+            break;
+        }
 
-    return caretRect;
+        RenderElement& current = downcast<RenderElement>(*firstLetter);
+        if (is<RenderListMarker>(current))
+            firstLetter = current.nextSibling();
+        else if (current.isFloatingOrOutOfFlowPositioned()) {
+            if (current.style().styleType() == FIRST_LETTER) {
+                firstLetter = current.firstChild();
+                break;
+            }
+            firstLetter = current.nextSibling();
+        } else if (current.isReplaced() || is<RenderButton>(current) || is<RenderMenuList>(current))
+            break;
+        else if (current.isFlexibleBoxIncludingDeprecated()
+#if ENABLE(CSS_GRID_LAYOUT)
+            || current.isRenderGrid()
+#endif
+            )
+            firstLetter = current.nextSibling();
+        else if (current.style().hasPseudoStyle(FIRST_LETTER) && current.canHaveGeneratedChildren())  {
+            // We found a lower-level node with first-letter, which supersedes the higher-level style
+            firstLetterContainer = &current;
+            firstLetter = current.firstChild();
+        } else
+            firstLetter = current.firstChild();
+    }
+    
+    if (!firstLetter)
+        firstLetterContainer = nullptr;
 }
 
-void RenderBlock::addFocusRingRects(Vector<IntRect>& rects, const LayoutPoint& additionalOffset, const RenderLayerModelObject* paintContainer)
+void RenderBlock::updateFirstLetter()
 {
-    // For blocks inside inlines, we go ahead and include margins so that we run right up to the
-    // inline boxes above and below us (thus getting merged with them to form a single irregular
-    // shape).
-    if (inlineElementContinuation()) {
-        // FIXME: This check really isn't accurate. 
-        bool nextInlineHasLineBox = inlineElementContinuation()->firstLineBox();
-        // FIXME: This is wrong. The principal renderer may not be the continuation preceding this block.
-        // FIXME: This is wrong for block-flows that are horizontal.
-        // https://bugs.webkit.org/show_bug.cgi?id=46781
-        bool prevInlineHasLineBox = toRenderInline(inlineElementContinuation()->node()->renderer())->firstLineBox(); 
-        float topMargin = prevInlineHasLineBox ? collapsedMarginBefore() : LayoutUnit();
-        float bottomMargin = nextInlineHasLineBox ? collapsedMarginAfter() : LayoutUnit();
-        LayoutRect rect(additionalOffset.x(), additionalOffset.y() - topMargin, width(), height() + topMargin + bottomMargin);
-        if (!rect.isEmpty())
-            rects.append(pixelSnappedIntRect(rect));
-    } else if (width() && height())
-        rects.append(pixelSnappedIntRect(additionalOffset, size()));
+    RenderObject* firstLetterObj;
+    RenderElement* firstLetterContainer;
+    // FIXME: The first letter might be composed of a variety of code units, and therefore might
+    // be contained within multiple RenderElements.
+    getFirstLetter(firstLetterObj, firstLetterContainer);
 
-    if (!hasOverflowClip() && !hasControlClip()) {
-        for (RootInlineBox* curr = firstRootBox(); curr; curr = curr->nextRootBox()) {
-            LayoutUnit top = max<LayoutUnit>(curr->lineTop(), curr->top());
-            LayoutUnit bottom = min<LayoutUnit>(curr->lineBottom(), curr->top() + curr->height());
-            LayoutRect rect(additionalOffset.x() + curr->x(), additionalOffset.y() + top, curr->width(), bottom - top);
-            if (!rect.isEmpty())
-                rects.append(pixelSnappedIntRect(rect));
-        }
+    if (!firstLetterObj || !firstLetterContainer)
+        return;
 
-        for (RenderObject* curr = firstChild(); curr; curr = curr->nextSibling()) {
-            if (!curr->isText() && !curr->isListMarker() && curr->isBox()) {
-                RenderBox* box = toRenderBox(curr);
-                FloatPoint pos;
-                // FIXME: This doesn't work correctly with transforms.
-                if (box->layer()) 
-                    pos = curr->localToContainerPoint(FloatPoint(), paintContainer);
-                else
-                    pos = FloatPoint(additionalOffset.x() + box->x(), additionalOffset.y() + box->y());
-                box->addFocusRingRects(rects, flooredLayoutPoint(pos), paintContainer);
-            }
-        }
+    // If the child already has style, then it has already been created, so we just want
+    // to update it.
+    if (firstLetterObj->parent()->style().styleType() == FIRST_LETTER) {
+        updateFirstLetterStyle(firstLetterContainer, firstLetterObj);
+        return;
     }
 
-    if (inlineElementContinuation())
-        inlineElementContinuation()->addFocusRingRects(rects, flooredLayoutPoint(additionalOffset + inlineElementContinuation()->containingBlock()->location() - location()), paintContainer);
+    if (!is<RenderText>(*firstLetterObj))
+        return;
+
+    // Our layout state is not valid for the repaints we are going to trigger by
+    // adding and removing children of firstLetterContainer.
+    LayoutStateDisabler layoutStateDisabler(view());
+
+    createFirstLetterRenderer(firstLetterContainer, downcast<RenderText>(firstLetterObj));
 }
 
-RenderBox* RenderBlock::createAnonymousBoxWithSameTypeAs(const RenderObject* parent) const
+RenderFlowThread* RenderBlock::cachedFlowThreadContainingBlock() const
 {
-    if (isAnonymousColumnsBlock())
-        return createAnonymousColumnsWithParentRenderer(parent);
-    if (isAnonymousColumnSpanBlock())
-        return createAnonymousColumnSpanWithParentRenderer(parent);
-    return createAnonymousWithParentRendererAndDisplay(parent, style()->display());
+    RenderBlockRareData* rareData = getBlockRareData(this);
+
+    if (!rareData || !rareData->m_flowThreadContainingBlock)
+        return nullptr;
+
+    return rareData->m_flowThreadContainingBlock.value();
 }
 
-bool RenderBlock::hasNextPage(LayoutUnit logicalOffset, PageBoundaryRule pageBoundaryRule) const
+bool RenderBlock::cachedFlowThreadContainingBlockNeedsUpdate() const
 {
-    ASSERT(view()->layoutState() && view()->layoutState()->isPaginated());
+    RenderBlockRareData* rareData = getBlockRareData(this);
 
-    RenderFlowThread* flowThread = flowThreadContainingBlock();
-    if (!flowThread)
-        return true; // Printing and multi-column both make new pages to accommodate content.
+    if (!rareData || !rareData->m_flowThreadContainingBlock)
+        return true;
 
-    // See if we're in the last region.
-    LayoutUnit pageOffset = offsetFromLogicalTopOfFirstPage() + logicalOffset;
-    RenderRegion* region = flowThread->regionAtBlockOffset(pageOffset, this);
-    if (!region)
-        return false;
-    if (region->isLastRegion())
-        return region->isRenderRegionSet() || region->style()->regionFragment() == BreakRegionFragment
-            || (pageBoundaryRule == IncludePageBoundary && pageOffset == region->logicalTopForFlowThreadContent());
-    return true;
+    return false;
 }
 
-LayoutUnit RenderBlock::nextPageLogicalTop(LayoutUnit logicalOffset, PageBoundaryRule pageBoundaryRule) const
+void RenderBlock::setCachedFlowThreadContainingBlockNeedsUpdate()
 {
-    LayoutUnit pageLogicalHeight = pageLogicalHeightForOffset(logicalOffset);
-    if (!pageLogicalHeight)
-        return logicalOffset;
-    
-    // The logicalOffset is in our coordinate space.  We can add in our pushed offset.
-    LayoutUnit remainingLogicalHeight = pageRemainingLogicalHeightForOffset(logicalOffset);
-    if (pageBoundaryRule == ExcludePageBoundary)
-        return logicalOffset + (remainingLogicalHeight ? remainingLogicalHeight : pageLogicalHeight);
-    return logicalOffset + remainingLogicalHeight;
+    RenderBlockRareData& rareData = ensureBlockRareData(this);
+    rareData.m_flowThreadContainingBlock = Nullopt;
 }
 
-static bool inNormalFlow(RenderBox* child)
+RenderFlowThread* RenderBlock::updateCachedFlowThreadContainingBlock(RenderFlowThread* flowThread) const
 {
-    RenderBlock* curr = child->containingBlock();
-    RenderView* renderView = child->view();
-    while (curr && curr != renderView) {
-        if (curr->hasColumns() || curr->isRenderFlowThread())
-            return true;
-        if (curr->isFloatingOrOutOfFlowPositioned())
-            return false;
-        curr = curr->containingBlock();
-    }
-    return true;
+    RenderBlockRareData& rareData = ensureBlockRareData(this);
+    rareData.m_flowThreadContainingBlock = flowThread;
+
+    return flowThread;
 }
 
-ColumnInfo::PaginationUnit RenderBlock::paginationUnit() const
+RenderFlowThread* RenderBlock::locateFlowThreadContainingBlock() const
 {
-    return ColumnInfo::Column;
+    RenderBlockRareData* rareData = getBlockRareData(this);
+    if (!rareData || !rareData->m_flowThreadContainingBlock)
+        return updateCachedFlowThreadContainingBlock(RenderBox::locateFlowThreadContainingBlock());
+
+    ASSERT(rareData->m_flowThreadContainingBlock.value() == RenderBox::locateFlowThreadContainingBlock());
+    return rareData->m_flowThreadContainingBlock.value();
 }
 
-LayoutUnit RenderBlock::applyBeforeBreak(RenderBox* child, LayoutUnit logicalOffset)
+LayoutUnit RenderBlock::paginationStrut() const
 {
-    // FIXME: Add page break checking here when we support printing.
-    bool checkColumnBreaks = view()->layoutState()->isPaginatingColumns();
-    bool checkPageBreaks = !checkColumnBreaks && view()->layoutState()->m_pageLogicalHeight; // FIXME: Once columns can print we have to check this.
-    RenderFlowThread* flowThread = flowThreadContainingBlock();
-    bool checkRegionBreaks = flowThread && flowThread->isRenderNamedFlowThread();
-    bool checkBeforeAlways = (checkColumnBreaks && child->style()->columnBreakBefore() == PBALWAYS) || (checkPageBreaks && child->style()->pageBreakBefore() == PBALWAYS)
-                             || (checkRegionBreaks && child->style()->regionBreakBefore() == PBALWAYS);
-    if (checkBeforeAlways && inNormalFlow(child) && hasNextPage(logicalOffset, IncludePageBoundary)) {
-        if (checkColumnBreaks)
-            view()->layoutState()->addForcedColumnBreak(child, logicalOffset);
-        if (checkRegionBreaks) {
-            LayoutUnit offsetBreakAdjustment = 0;
-            if (flowThread->addForcedRegionBreak(offsetFromLogicalTopOfFirstPage() + logicalOffset, child, true, &offsetBreakAdjustment))
-                return logicalOffset + offsetBreakAdjustment;
-        }
-        return nextPageLogicalTop(logicalOffset, IncludePageBoundary);
-    }
-    return logicalOffset;
+    RenderBlockRareData* rareData = getBlockRareData(this);
+    return rareData ? rareData->m_paginationStrut : LayoutUnit();
 }
 
-LayoutUnit RenderBlock::applyAfterBreak(RenderBox* child, LayoutUnit logicalOffset, MarginInfo& marginInfo)
+LayoutUnit RenderBlock::pageLogicalOffset() const
 {
-    // FIXME: Add page break checking here when we support printing.
-    bool checkColumnBreaks = view()->layoutState()->isPaginatingColumns();
-    bool checkPageBreaks = !checkColumnBreaks && view()->layoutState()->m_pageLogicalHeight; // FIXME: Once columns can print we have to check this.
-    RenderFlowThread* flowThread = flowThreadContainingBlock();
-    bool checkRegionBreaks = flowThread && flowThread->isRenderNamedFlowThread();
-    bool checkAfterAlways = (checkColumnBreaks && child->style()->columnBreakAfter() == PBALWAYS) || (checkPageBreaks && child->style()->pageBreakAfter() == PBALWAYS)
-                            || (checkRegionBreaks && child->style()->regionBreakAfter() == PBALWAYS);
-    if (checkAfterAlways && inNormalFlow(child) && hasNextPage(logicalOffset, IncludePageBoundary)) {
-        LayoutUnit marginOffset = marginInfo.canCollapseWithMarginBefore() ? LayoutUnit() : marginInfo.margin();
-
-        // So our margin doesn't participate in the next collapsing steps.
-        marginInfo.clearMargin();
-
-        if (checkColumnBreaks)
-            view()->layoutState()->addForcedColumnBreak(child, logicalOffset);
-        if (checkRegionBreaks) {
-            LayoutUnit offsetBreakAdjustment = 0;
-            if (flowThread->addForcedRegionBreak(offsetFromLogicalTopOfFirstPage() + logicalOffset + marginOffset, child, false, &offsetBreakAdjustment))
-                return logicalOffset + marginOffset + offsetBreakAdjustment;
-        }
-        return nextPageLogicalTop(logicalOffset, IncludePageBoundary);
+    RenderBlockRareData* rareData = getBlockRareData(this);
+    return rareData ? rareData->m_pageLogicalOffset : LayoutUnit();
+}
+
+void RenderBlock::setPaginationStrut(LayoutUnit strut)
+{
+    RenderBlockRareData* rareData = getBlockRareData(this);
+    if (!rareData) {
+        if (!strut)
+            return;
+        rareData = &ensureBlockRareData(this);
     }
-    return logicalOffset;
+    rareData->m_paginationStrut = strut;
 }
 
-LayoutUnit RenderBlock::pageLogicalTopForOffset(LayoutUnit offset) const
+void RenderBlock::setPageLogicalOffset(LayoutUnit logicalOffset)
 {
-    RenderView* renderView = view();
-    LayoutUnit firstPageLogicalTop = isHorizontalWritingMode() ? renderView->layoutState()->m_pageOffset.height() : renderView->layoutState()->m_pageOffset.width();
-    LayoutUnit blockLogicalTop = isHorizontalWritingMode() ? renderView->layoutState()->m_layoutOffset.height() : renderView->layoutState()->m_layoutOffset.width();
-
-    LayoutUnit cumulativeOffset = offset + blockLogicalTop;
-    RenderFlowThread* flowThread = flowThreadContainingBlock();
-    if (!flowThread) {
-        LayoutUnit pageLogicalHeight = renderView->layoutState()->pageLogicalHeight();
-        if (!pageLogicalHeight)
-            return 0;
-        return cumulativeOffset - roundToInt(cumulativeOffset - firstPageLogicalTop) % roundToInt(pageLogicalHeight);
+    RenderBlockRareData* rareData = getBlockRareData(this);
+    if (!rareData) {
+        if (!logicalOffset)
+            return;
+        rareData = &ensureBlockRareData(this);
     }
-    return flowThread->pageLogicalTopForOffset(cumulativeOffset);
+    rareData->m_pageLogicalOffset = logicalOffset;
 }
 
-LayoutUnit RenderBlock::pageLogicalHeightForOffset(LayoutUnit offset) const
+void RenderBlock::absoluteRects(Vector<IntRect>& rects, const LayoutPoint& accumulatedOffset) const
 {
-    RenderView* renderView = view();
-    RenderFlowThread* flowThread = flowThreadContainingBlock();
-    if (!flowThread)
-        return renderView->layoutState()->m_pageLogicalHeight;
-    return flowThread->pageLogicalHeightForOffset(offset + offsetFromLogicalTopOfFirstPage());
+    // For blocks inside inlines, we include margins so that we run right up to the inline boxes
+    // above and below us (thus getting merged with them to form a single irregular shape).
+    if (isAnonymousBlockContinuation()) {
+        // FIXME: This is wrong for block-flows that are horizontal.
+        // https://bugs.webkit.org/show_bug.cgi?id=46781
+        rects.append(snappedIntRect(accumulatedOffset.x(), accumulatedOffset.y() - collapsedMarginBefore(),
+                                width(), height() + collapsedMarginBefore() + collapsedMarginAfter()));
+        continuation()->absoluteRects(rects, accumulatedOffset - toLayoutSize(location() +
+                inlineElementContinuation()->containingBlock()->location()));
+    } else
+        rects.append(snappedIntRect(accumulatedOffset, size()));
 }
 
-LayoutUnit RenderBlock::pageRemainingLogicalHeightForOffset(LayoutUnit offset, PageBoundaryRule pageBoundaryRule) const
+void RenderBlock::absoluteQuads(Vector<FloatQuad>& quads, bool* wasFixed) const
 {
-    RenderView* renderView = view();
-    offset += offsetFromLogicalTopOfFirstPage();
+    // For blocks inside inlines, we include margins so that we run right up to the inline boxes
+    // above and below us (thus getting merged with them to form a single irregular shape).
+    FloatRect localRect = isAnonymousBlockContinuation() 
+        ? FloatRect(0, -collapsedMarginBefore(), width(), height() + collapsedMarginBefore() + collapsedMarginAfter())
+        : FloatRect(0, 0, width(), height());
     
+    // FIXME: This is wrong for block-flows that are horizontal.
+    // https://bugs.webkit.org/show_bug.cgi?id=46781
     RenderFlowThread* flowThread = flowThreadContainingBlock();
-    if (!flowThread) {
-        LayoutUnit pageLogicalHeight = renderView->layoutState()->m_pageLogicalHeight;
-        LayoutUnit remainingHeight = pageLogicalHeight - intMod(offset, pageLogicalHeight);
-        if (pageBoundaryRule == IncludePageBoundary) {
-            // If includeBoundaryPoint is true the line exactly on the top edge of a
-            // column will act as being part of the previous column.
-            remainingHeight = intMod(remainingHeight, pageLogicalHeight);
-        }
-        return remainingHeight;
-    }
-    
-    return flowThread->pageRemainingLogicalHeightForOffset(offset, pageBoundaryRule);
+    if (!flowThread || !flowThread->absoluteQuadsForBox(quads, wasFixed, this, localRect.y(), localRect.maxY()))
+        quads.append(localToAbsoluteQuad(localRect, UseTransforms, wasFixed));
+
+    if (isAnonymousBlockContinuation())
+        continuation()->absoluteQuads(quads, wasFixed);
 }
 
-LayoutUnit RenderBlock::adjustForUnsplittableChild(RenderBox* child, LayoutUnit logicalOffset, bool includeMargins)
+LayoutRect RenderBlock::rectWithOutlineForRepaint(const RenderLayerModelObject* repaintContainer, LayoutUnit outlineWidth) const
 {
-    bool checkColumnBreaks = view()->layoutState()->isPaginatingColumns();
-    bool checkPageBreaks = !checkColumnBreaks && view()->layoutState()->m_pageLogicalHeight;
-    RenderFlowThread* flowThread = flowThreadContainingBlock();
-    bool checkRegionBreaks = flowThread && flowThread->isRenderNamedFlowThread();
-    bool isUnsplittable = child->isUnsplittableForPagination() || (checkColumnBreaks && child->style()->columnBreakInside() == PBAVOID)
-        || (checkPageBreaks && child->style()->pageBreakInside() == PBAVOID)
-        || (checkRegionBreaks && child->style()->regionBreakInside() == PBAVOID);
-    if (!isUnsplittable)
-        return logicalOffset;
-    LayoutUnit childLogicalHeight = logicalHeightForChild(child) + (includeMargins ? marginBeforeForChild(child) + marginAfterForChild(child) : LayoutUnit());
-    LayoutUnit pageLogicalHeight = pageLogicalHeightForOffset(logicalOffset);
-    bool hasUniformPageLogicalHeight = !flowThread || flowThread->regionsHaveUniformLogicalHeight();
-    updateMinimumPageHeight(logicalOffset, childLogicalHeight);
-    if (!pageLogicalHeight || (hasUniformPageLogicalHeight && childLogicalHeight > pageLogicalHeight)
-        || !hasNextPage(logicalOffset))
-        return logicalOffset;
-    LayoutUnit remainingLogicalHeight = pageRemainingLogicalHeightForOffset(logicalOffset, ExcludePageBoundary);
-    if (remainingLogicalHeight < childLogicalHeight) {
-        if (!hasUniformPageLogicalHeight && !pushToNextPageWithMinimumLogicalHeight(remainingLogicalHeight, logicalOffset, childLogicalHeight))
-            return logicalOffset;
-        return logicalOffset + remainingLogicalHeight;
-    }
-    return logicalOffset;
+    LayoutRect r(RenderBox::rectWithOutlineForRepaint(repaintContainer, outlineWidth));
+    if (isAnonymousBlockContinuation())
+        r.inflateY(collapsedMarginBefore()); // FIXME: This is wrong for block-flows that are horizontal.
+    return r;
 }
 
-bool RenderBlock::pushToNextPageWithMinimumLogicalHeight(LayoutUnit& adjustment, LayoutUnit logicalOffset, LayoutUnit minimumLogicalHeight) const
+RenderElement* RenderBlock::hoverAncestor() const
 {
-    bool checkRegion = false;
-    for (LayoutUnit pageLogicalHeight = pageLogicalHeightForOffset(logicalOffset + adjustment); pageLogicalHeight;
-        pageLogicalHeight = pageLogicalHeightForOffset(logicalOffset + adjustment)) {
-        if (minimumLogicalHeight <= pageLogicalHeight)
-            return true;
-        if (!hasNextPage(logicalOffset + adjustment))
-            return false;
-        adjustment += pageLogicalHeight;
-        checkRegion = true;
-    }
-    return !checkRegion;
+    return isAnonymousBlockContinuation() ? continuation() : RenderBox::hoverAncestor();
 }
 
-void RenderBlock::setPageBreak(LayoutUnit offset, LayoutUnit spaceShortage)
+void RenderBlock::updateDragState(bool dragOn)
 {
-    if (RenderFlowThread* flowThread = flowThreadContainingBlock())
-        flowThread->setPageBreak(offsetFromLogicalTopOfFirstPage() + offset, spaceShortage);
+    RenderBox::updateDragState(dragOn);
+    if (RenderBoxModelObject* continuation = this->continuation())
+        continuation->updateDragState(dragOn);
 }
 
-void RenderBlock::updateMinimumPageHeight(LayoutUnit offset, LayoutUnit minHeight)
+const RenderStyle& RenderBlock::outlineStyleForRepaint() const
 {
-    if (RenderFlowThread* flowThread = flowThreadContainingBlock())
-        flowThread->updateMinimumPageHeight(offsetFromLogicalTopOfFirstPage() + offset, minHeight);
-    else if (ColumnInfo* colInfo = view()->layoutState()->m_columnInfo)
-        colInfo->updateMinimumColumnHeight(minHeight);
+    return isAnonymousBlockContinuation() ? continuation()->style() : RenderElement::outlineStyleForRepaint();
 }
 
-static inline LayoutUnit calculateMinimumPageHeight(RenderStyle* renderStyle, RootInlineBox* lastLine, LayoutUnit lineTop, LayoutUnit lineBottom)
+void RenderBlock::childBecameNonInline(RenderElement&)
 {
-    // We may require a certain minimum number of lines per page in order to satisfy
-    // orphans and widows, and that may affect the minimum page height.
-    unsigned lineCount = max<unsigned>(renderStyle->hasAutoOrphans() ? 1 : renderStyle->orphans(), renderStyle->hasAutoWidows() ? 1 : renderStyle->widows());
-    if (lineCount > 1) {
-        RootInlineBox* line = lastLine;
-        for (unsigned i = 1; i < lineCount && line->prevRootBox(); i++)
-            line = line->prevRootBox();
-
-        // FIXME: Paginating using line overflow isn't all fine. See FIXME in
-        // adjustLinePositionForPagination() for more details.
-        LayoutRect overflow = line->logicalVisualOverflowRect(line->lineTop(), line->lineBottom());
-        lineTop = min(line->lineTopWithLeading(), overflow.y());
-    }
-    return lineBottom - lineTop;
+    makeChildrenNonInline();
+    if (isAnonymousBlock() && is<RenderBlock>(parent()))
+        downcast<RenderBlock>(*parent()).removeLeftoverAnonymousBlock(this);
+    // |this| may be dead here
 }
 
-void RenderBlock::adjustLinePositionForPagination(RootInlineBox* lineBox, LayoutUnit& delta, RenderFlowThread* flowThread)
+void RenderBlock::updateHitTestResult(HitTestResult& result, const LayoutPoint& point)
 {
-    // FIXME: For now we paginate using line overflow.  This ensures that lines don't overlap at all when we
-    // put a strut between them for pagination purposes.  However, this really isn't the desired rendering, since
-    // the line on the top of the next page will appear too far down relative to the same kind of line at the top
-    // of the first column.
-    //
-    // The rendering we would like to see is one where the lineTopWithLeading is at the top of the column, and any line overflow
-    // simply spills out above the top of the column.  This effect would match what happens at the top of the first column.
-    // We can't achieve this rendering, however, until we stop columns from clipping to the column bounds (thus allowing
-    // for overflow to occur), and then cache visible overflow for each column rect.
-    //
-    // Furthermore, the paint we have to do when a column has overflow has to be special.  We need to exclude
-    // content that paints in a previous column (and content that paints in the following column).
-    //
-    // For now we'll at least honor the lineTopWithLeading when paginating if it is above the logical top overflow. This will
-    // at least make positive leading work in typical cases.
-    //
-    // FIXME: Another problem with simply moving lines is that the available line width may change (because of floats).
-    // Technically if the location we move the line to has a different line width than our old position, then we need to dirty the
-    // line and all following lines.
-    LayoutRect logicalVisualOverflow = lineBox->logicalVisualOverflowRect(lineBox->lineTop(), lineBox->lineBottom());
-    LayoutUnit logicalOffset = min(lineBox->lineTopWithLeading(), logicalVisualOverflow.y());
-    LayoutUnit logicalBottom = max(lineBox->lineBottomWithLeading(), logicalVisualOverflow.maxY());
-    LayoutUnit lineHeight = logicalBottom - logicalOffset;
-    updateMinimumPageHeight(logicalOffset, calculateMinimumPageHeight(style(), lineBox, logicalOffset, logicalBottom));
-    logicalOffset += delta;
-    lineBox->setPaginationStrut(0);
-    lineBox->setIsFirstAfterPageBreak(false);
-    LayoutUnit pageLogicalHeight = pageLogicalHeightForOffset(logicalOffset);
-    bool hasUniformPageLogicalHeight = !flowThread || flowThread->regionsHaveUniformLogicalHeight();
-    // If lineHeight is greater than pageLogicalHeight, but logicalVisualOverflow.height() still fits, we are
-    // still going to add a strut, so that the visible overflow fits on a single page.
-    if (!pageLogicalHeight || (hasUniformPageLogicalHeight && logicalVisualOverflow.height() > pageLogicalHeight)
-        || !hasNextPage(logicalOffset))
+    if (result.innerNode())
         return;
-    LayoutUnit remainingLogicalHeight = pageRemainingLogicalHeightForOffset(logicalOffset, ExcludePageBoundary);
 
-    if (remainingLogicalHeight < lineHeight || (shouldBreakAtLineToAvoidWidow() && lineBreakToAvoidWidow() == lineBox)) {
-        if (shouldBreakAtLineToAvoidWidow() && lineBreakToAvoidWidow() == lineBox)
-            clearShouldBreakAtLineToAvoidWidow();
-        // If we have a non-uniform page height, then we have to shift further possibly.
-        if (!hasUniformPageLogicalHeight && !pushToNextPageWithMinimumLogicalHeight(remainingLogicalHeight, logicalOffset, lineHeight))
-            return;
-        if (lineHeight > pageLogicalHeight) {
-            // Split the top margin in order to avoid splitting the visible part of the line.
-            remainingLogicalHeight -= min(lineHeight - pageLogicalHeight, max<LayoutUnit>(0, logicalVisualOverflow.y() - lineBox->lineTopWithLeading()));
-        }
-        LayoutUnit totalLogicalHeight = lineHeight + max<LayoutUnit>(0, logicalOffset);
-        LayoutUnit pageLogicalHeightAtNewOffset = hasUniformPageLogicalHeight ? pageLogicalHeight : pageLogicalHeightForOffset(logicalOffset + remainingLogicalHeight);
-        setPageBreak(logicalOffset, lineHeight - remainingLogicalHeight);
-        if (((lineBox == firstRootBox() && totalLogicalHeight < pageLogicalHeightAtNewOffset) || (!style()->hasAutoOrphans() && style()->orphans() >= lineCount(lineBox)))
-            && !isOutOfFlowPositioned() && !isTableCell())
-            setPaginationStrut(remainingLogicalHeight + max<LayoutUnit>(0, logicalOffset));
-        else {
-            delta += remainingLogicalHeight;
-            lineBox->setPaginationStrut(remainingLogicalHeight);
-            lineBox->setIsFirstAfterPageBreak(true);
-        }
-    } else if (remainingLogicalHeight == pageLogicalHeight && lineBox != firstRootBox())
-        lineBox->setIsFirstAfterPageBreak(true);
+    if (Node* n = nodeForHitTest()) {
+        result.setInnerNode(n);
+        if (!result.innerNonSharedNode())
+            result.setInnerNonSharedNode(n);
+        result.setLocalPoint(point);
+    }
 }
 
-LayoutUnit RenderBlock::adjustBlockChildForPagination(LayoutUnit logicalTopAfterClear, LayoutUnit estimateWithoutPagination, RenderBox* child, bool atBeforeSideOfBlock)
+LayoutRect RenderBlock::localCaretRect(InlineBox* inlineBox, int caretOffset, LayoutUnit* extraWidthToEndOfLine)
 {
-    RenderBlock* childRenderBlock = child->isRenderBlock() ? toRenderBlock(child) : 0;
+    // Do the normal calculation in most cases.
+    if (firstChild())
+        return RenderBox::localCaretRect(inlineBox, caretOffset, extraWidthToEndOfLine);
 
-    if (estimateWithoutPagination != logicalTopAfterClear) {
-        // Our guess prior to pagination movement was wrong. Before we attempt to paginate, let's try again at the new
-        // position.
-        setLogicalHeight(logicalTopAfterClear);
-        setLogicalTopForChild(child, logicalTopAfterClear, ApplyLayoutDelta);
+    LayoutRect caretRect = localCaretRectForEmptyElement(width(), textIndentOffset());
 
-        if (child->shrinkToAvoidFloats()) {
-            // The child's width depends on the line width.
-            // When the child shifts to clear an item, its width can
-            // change (because it has more available line width).
-            // So go ahead and mark the item as dirty.
-            child->setChildNeedsLayout(true, MarkOnlyThis);
-        }
-        
-        if (childRenderBlock) {
-            if (!child->avoidsFloats() && childRenderBlock->containsFloats())
-                childRenderBlock->markAllDescendantsWithFloatsForLayout();
-            if (!child->needsLayout())
-                child->markForPaginationRelayoutIfNeeded();
-        }
+    // FIXME: Does this need to adjust for vertical orientation?
+    if (extraWidthToEndOfLine)
+        *extraWidthToEndOfLine = width() - caretRect.maxX();
 
-        // Our guess was wrong. Make the child lay itself out again.
-        child->layoutIfNeeded();
-    }
+    return caretRect;
+}
 
-    LayoutUnit oldTop = logicalTopAfterClear;
-
-    // If the object has a page or column break value of "before", then we should shift to the top of the next page.
-    LayoutUnit result = applyBeforeBreak(child, logicalTopAfterClear);
-
-    if (pageLogicalHeightForOffset(result)) {
-        LayoutUnit remainingLogicalHeight = pageRemainingLogicalHeightForOffset(result, ExcludePageBoundary);
-        LayoutUnit spaceShortage = child->logicalHeight() - remainingLogicalHeight;
-        if (spaceShortage > 0) {
-            // If the child crosses a column boundary, report a break, in case nothing inside it has already
-            // done so. The column balancer needs to know how much it has to stretch the columns to make more
-            // content fit. If no breaks are reported (but do occur), the balancer will have no clue. FIXME:
-            // This should be improved, though, because here we just pretend that the child is
-            // unsplittable. A splittable child, on the other hand, has break opportunities at every position
-            // where there's no child content, border or padding. In other words, we risk stretching more
-            // than necessary.
-            setPageBreak(result, spaceShortage);
-        }
-    }
+void RenderBlock::addFocusRingRectsForInlineChildren(Vector<LayoutRect>&, const LayoutPoint&, const RenderLayerModelObject*)
+{
+    ASSERT_NOT_REACHED();
+}
+
+void RenderBlock::addFocusRingRects(Vector<LayoutRect>& rects, const LayoutPoint& additionalOffset, const RenderLayerModelObject* paintContainer)
+{
+    // For blocks inside inlines, we include margins so that we run right up to the inline boxes
+    // above and below us (thus getting merged with them to form a single irregular shape).
+    if (inlineElementContinuation()) {
+        // FIXME: This check really isn't accurate. 
+        bool nextInlineHasLineBox = inlineElementContinuation()->firstLineBox();
+        // FIXME: This is wrong. The principal renderer may not be the continuation preceding this block.
+        // FIXME: This is wrong for block-flows that are horizontal.
+        // https://bugs.webkit.org/show_bug.cgi?id=46781
+        bool prevInlineHasLineBox = downcast<RenderInline>(*inlineElementContinuation()->element()->renderer()).firstLineBox();
+        float topMargin = prevInlineHasLineBox ? collapsedMarginBefore() : LayoutUnit();
+        float bottomMargin = nextInlineHasLineBox ? collapsedMarginAfter() : LayoutUnit();
+        LayoutRect rect(additionalOffset.x(), additionalOffset.y() - topMargin, width(), height() + topMargin + bottomMargin);
+        if (!rect.isEmpty())
+            rects.append(rect);
+    } else if (width() && height())
+        rects.append(LayoutRect(additionalOffset, size()));
 
-    // For replaced elements and scrolled elements, we want to shift them to the next page if they don't fit on the current one.
-    LayoutUnit logicalTopBeforeUnsplittableAdjustment = result;
-    LayoutUnit logicalTopAfterUnsplittableAdjustment = adjustForUnsplittableChild(child, result);
+    if (!hasOverflowClip() && !hasControlClip()) {
+        if (childrenInline())
+            addFocusRingRectsForInlineChildren(rects, additionalOffset, paintContainer);
     
-    LayoutUnit paginationStrut = 0;
-    LayoutUnit unsplittableAdjustmentDelta = logicalTopAfterUnsplittableAdjustment - logicalTopBeforeUnsplittableAdjustment;
-    if (unsplittableAdjustmentDelta)
-        paginationStrut = unsplittableAdjustmentDelta;
-    else if (childRenderBlock && childRenderBlock->paginationStrut())
-        paginationStrut = childRenderBlock->paginationStrut();
-
-    if (paginationStrut) {
-        // We are willing to propagate out to our parent block as long as we were at the top of the block prior
-        // to collapsing our margins, and as long as we didn't clear or move as a result of other pagination.
-        if (atBeforeSideOfBlock && oldTop == result && !isOutOfFlowPositioned() && !isTableCell()) {
-            // FIXME: Should really check if we're exceeding the page height before propagating the strut, but we don't
-            // have all the information to do so (the strut only has the remaining amount to push). Gecko gets this wrong too
-            // and pushes to the next page anyway, so not too concerned about it.
-            setPaginationStrut(result + paginationStrut);
-            if (childRenderBlock)
-                childRenderBlock->setPaginationStrut(0);
-        } else
-            result += paginationStrut;
+        for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
+            if (!is<RenderText>(*child) && !is<RenderListMarker>(*child) && is<RenderBox>(*child)) {
+                auto& box = downcast<RenderBox>(*child);
+                FloatPoint pos;
+                // FIXME: This doesn't work correctly with transforms.
+                if (box.layer())
+                    pos = child->localToContainerPoint(FloatPoint(), paintContainer);
+                else
+                    pos = FloatPoint(additionalOffset.x() + box.x(), additionalOffset.y() + box.y());
+                box.addFocusRingRects(rects, flooredLayoutPoint(pos), paintContainer);
+            }
+        }
     }
 
-    // Similar to how we apply clearance. Go ahead and boost height() to be the place where we're going to position the child.
-    setLogicalHeight(logicalHeight() + (result - oldTop));
-    
-    // Return the final adjusted logical top.
-    return result;
+    if (inlineElementContinuation())
+        inlineElementContinuation()->addFocusRingRects(rects, flooredLayoutPoint(LayoutPoint(additionalOffset + inlineElementContinuation()->containingBlock()->location() - location())), paintContainer);
 }
 
-bool RenderBlock::lineWidthForPaginatedLineChanged(RootInlineBox* rootBox, LayoutUnit lineDelta, RenderFlowThread* flowThread) const
+RenderBox* RenderBlock::createAnonymousBoxWithSameTypeAs(const RenderObject* parent) const
 {
-    if (!flowThread)
-        return false;
-
-    RenderRegion* currentRegion = regionAtBlockOffset(rootBox->lineTopWithLeading() + lineDelta);
-    // Just bail if the region didn't change.
-    if (rootBox->containingRegion() == currentRegion)
-        return false;
-    return rootBox->paginatedLineWidth() != availableLogicalWidthForContent(currentRegion);
+    return createAnonymousWithParentRendererAndDisplay(parent, style().display());
 }
 
 LayoutUnit RenderBlock::offsetFromLogicalTopOfFirstPage() const
 {
-    LayoutState* layoutState = view()->layoutState();
+    LayoutState* layoutState = view().layoutState();
     if (layoutState && !layoutState->isPaginated())
         return 0;
 
@@ -7793,201 +3513,187 @@ RenderRegion* RenderBlock::regionAtBlockOffset(LayoutUnit blockOffset) const
     if (!flowThread || !flowThread->hasValidRegionInfo())
         return 0;
 
-    return flowThread->regionAtBlockOffset(offsetFromLogicalTopOfFirstPage() + blockOffset, true);
+    return flowThread->regionAtBlockOffset(this, offsetFromLogicalTopOfFirstPage() + blockOffset, true);
 }
 
-void RenderBlock::updateStaticInlinePositionForChild(RenderBox* child, LayoutUnit logicalTop)
+static bool canComputeRegionRangeForBox(const RenderBlock* parentBlock, const RenderBox& childBox, const RenderFlowThread* flowThreadContainingBlock)
 {
-    if (child->style()->isOriginalDisplayInlineType())
-        setStaticInlinePositionForChild(child, logicalTop, startAlignedOffsetForLine(logicalTop, false));
-    else
-        setStaticInlinePositionForChild(child, logicalTop, startOffsetForContent(logicalTop));
+    ASSERT(parentBlock);
+    ASSERT(!childBox.isRenderNamedFlowThread());
+
+    if (!flowThreadContainingBlock)
+        return false;
+
+    if (!flowThreadContainingBlock->hasRegions())
+        return false;
+
+    if (!childBox.canHaveOutsideRegionRange())
+        return false;
+
+    return flowThreadContainingBlock->hasCachedRegionRangeForBox(parentBlock);
+}
+
+bool RenderBlock::childBoxIsUnsplittableForFragmentation(const RenderBox& child) const
+{
+    RenderFlowThread* flowThread = flowThreadContainingBlock();
+    bool checkColumnBreaks = flowThread && flowThread->shouldCheckColumnBreaks();
+    bool checkPageBreaks = !checkColumnBreaks && view().layoutState()->m_pageLogicalHeight;
+    bool checkRegionBreaks = flowThread && flowThread->isRenderNamedFlowThread();
+    return child.isUnsplittableForPagination() || child.style().breakInside() == AvoidBreakInside
+        || (checkColumnBreaks && child.style().breakInside() == AvoidColumnBreakInside)
+        || (checkPageBreaks && child.style().breakInside() == AvoidPageBreakInside)
+        || (checkRegionBreaks && child.style().breakInside() == AvoidRegionBreakInside);
 }
 
-void RenderBlock::setStaticInlinePositionForChild(RenderBox* child, LayoutUnit blockOffset, LayoutUnit inlinePosition)
+void RenderBlock::computeRegionRangeForBoxChild(const RenderBox& box) const
 {
-    if (flowThreadContainingBlock()) {
-        // Shift the inline position to exclude the region offset.
-        inlinePosition += startOffsetForContent() - startOffsetForContent(blockOffset);
+    RenderFlowThread* flowThread = flowThreadContainingBlock();
+    ASSERT(canComputeRegionRangeForBox(this, box, flowThread));
+
+    RenderRegion* startRegion;
+    RenderRegion* endRegion;
+    LayoutUnit offsetFromLogicalTopOfFirstRegion = box.offsetFromLogicalTopOfFirstPage();
+    if (childBoxIsUnsplittableForFragmentation(box))
+        startRegion = endRegion = flowThread->regionAtBlockOffset(this, offsetFromLogicalTopOfFirstRegion, true);
+    else {
+        startRegion = flowThread->regionAtBlockOffset(this, offsetFromLogicalTopOfFirstRegion, true);
+        endRegion = flowThread->regionAtBlockOffset(this, offsetFromLogicalTopOfFirstRegion + logicalHeightForChild(box), true);
     }
-    child->layer()->setStaticInlinePosition(inlinePosition);
+
+    flowThread->setRegionRangeForBox(&box, startRegion, endRegion);
 }
 
-bool RenderBlock::logicalWidthChangedInRegions(RenderFlowThread* flowThread) const
+void RenderBlock::estimateRegionRangeForBoxChild(const RenderBox& box) const
 {
-    if (!flowThread || !flowThread->hasValidRegionInfo())
-        return false;
-    
-    return flowThread->logicalWidthChangedInRegionsForBlock(this);
+    RenderFlowThread* flowThread = flowThreadContainingBlock();
+    if (!canComputeRegionRangeForBox(this, box, flowThread))
+        return;
+
+    if (childBoxIsUnsplittableForFragmentation(box)) {
+        computeRegionRangeForBoxChild(box);
+        return;
+    }
+
+    LogicalExtentComputedValues estimatedValues;
+    box.computeLogicalHeight(RenderFlowThread::maxLogicalHeight(), logicalTopForChild(box), estimatedValues);
+
+    LayoutUnit offsetFromLogicalTopOfFirstRegion = box.offsetFromLogicalTopOfFirstPage();
+    RenderRegion* startRegion = flowThread->regionAtBlockOffset(this, offsetFromLogicalTopOfFirstRegion, true);
+    RenderRegion* endRegion = flowThread->regionAtBlockOffset(this, offsetFromLogicalTopOfFirstRegion + estimatedValues.m_extent, true);
+
+    flowThread->setRegionRangeForBox(&box, startRegion, endRegion);
 }
 
-RenderRegion* RenderBlock::clampToStartAndEndRegions(RenderRegion* region) const
+bool RenderBlock::updateRegionRangeForBoxChild(const RenderBox& box) const
 {
     RenderFlowThread* flowThread = flowThreadContainingBlock();
+    if (!canComputeRegionRangeForBox(this, box, flowThread))
+        return false;
 
-    ASSERT(isRenderView() || (region && flowThread));
-    if (isRenderView())
-        return region;
+    RenderRegion* startRegion = nullptr;
+    RenderRegion* endRegion = nullptr;
+    flowThread->getRegionRangeForBox(&box, startRegion, endRegion);
 
-    // We need to clamp to the block, since we want any lines or blocks that overflow out of the
-    // logical top or logical bottom of the block to size as though the border box in the first and
-    // last regions extended infinitely. Otherwise the lines are going to size according to the regions
-    // they overflow into, which makes no sense when this block doesn't exist in |region| at all.
-    RenderRegion* startRegion;
-    RenderRegion* endRegion;
-    flowThread->getRegionRangeForBox(this, startRegion, endRegion);
-    
-    if (startRegion && region->logicalTopForFlowThreadContent() < startRegion->logicalTopForFlowThreadContent())
-        return startRegion;
-    if (endRegion && region->logicalTopForFlowThreadContent() > endRegion->logicalTopForFlowThreadContent())
-        return endRegion;
-    
-    return region;
+    computeRegionRangeForBoxChild(box);
+
+    RenderRegion* newStartRegion = nullptr;
+    RenderRegion* newEndRegion = nullptr;
+    flowThread->getRegionRangeForBox(&box, newStartRegion, newEndRegion);
+
+
+    // Changing the start region means we shift everything and a relayout is needed.
+    if (newStartRegion != startRegion)
+        return true;
+
+    // The region range of the box has changed. Some boxes (e.g floats) may have been positioned assuming
+    // a different range.
+    if (box.needsLayoutAfterRegionRangeChange() && newEndRegion != endRegion)
+        return true;
+
+    return false;
 }
 
-LayoutUnit RenderBlock::collapsedMarginBeforeForChild(const RenderBox* child) const
+LayoutUnit RenderBlock::collapsedMarginBeforeForChild(const RenderBox& child) const
 {
     // If the child has the same directionality as we do, then we can just return its
     // collapsed margin.
-    if (!child->isWritingModeRoot())
-        return child->collapsedMarginBefore();
+    if (!child.isWritingModeRoot())
+        return child.collapsedMarginBefore();
     
     // The child has a different directionality.  If the child is parallel, then it's just
     // flipped relative to us.  We can use the collapsed margin for the opposite edge.
-    if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
-        return child->collapsedMarginAfter();
+    if (child.isHorizontalWritingMode() == isHorizontalWritingMode())
+        return child.collapsedMarginAfter();
     
     // The child is perpendicular to us, which means its margins don't collapse but are on the
     // "logical left/right" sides of the child box.  We can just return the raw margin in this case.  
     return marginBeforeForChild(child);
 }
 
-LayoutUnit RenderBlock::collapsedMarginAfterForChild(const  RenderBox* child) const
+LayoutUnit RenderBlock::collapsedMarginAfterForChild(const RenderBox& child) const
 {
     // If the child has the same directionality as we do, then we can just return its
     // collapsed margin.
-    if (!child->isWritingModeRoot())
-        return child->collapsedMarginAfter();
+    if (!child.isWritingModeRoot())
+        return child.collapsedMarginAfter();
     
     // The child has a different directionality.  If the child is parallel, then it's just
     // flipped relative to us.  We can use the collapsed margin for the opposite edge.
-    if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
-        return child->collapsedMarginBefore();
+    if (child.isHorizontalWritingMode() == isHorizontalWritingMode())
+        return child.collapsedMarginBefore();
     
     // The child is perpendicular to us, which means its margins don't collapse but are on the
     // "logical left/right" side of the child box.  We can just return the raw margin in this case.  
     return marginAfterForChild(child);
 }
 
-bool RenderBlock::hasMarginBeforeQuirk(const RenderBox* child) const
+bool RenderBlock::hasMarginBeforeQuirk(const RenderBox& child) const
 {
     // If the child has the same directionality as we do, then we can just return its
     // margin quirk.
-    if (!child->isWritingModeRoot())
-        return child->isRenderBlock() ? toRenderBlock(child)->hasMarginBeforeQuirk() : child->style()->hasMarginBeforeQuirk();
+    if (!child.isWritingModeRoot())
+        return is<RenderBlock>(child) ? downcast<RenderBlock>(child).hasMarginBeforeQuirk() : child.style().hasMarginBeforeQuirk();
     
     // The child has a different directionality. If the child is parallel, then it's just
     // flipped relative to us. We can use the opposite edge.
-    if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
-        return child->isRenderBlock() ? toRenderBlock(child)->hasMarginAfterQuirk() : child->style()->hasMarginAfterQuirk();
+    if (child.isHorizontalWritingMode() == isHorizontalWritingMode())
+        return is<RenderBlock>(child) ? downcast<RenderBlock>(child).hasMarginAfterQuirk() : child.style().hasMarginAfterQuirk();
     
     // The child is perpendicular to us and box sides are never quirky in html.css, and we don't really care about
     // whether or not authors specified quirky ems, since they're an implementation detail.
     return false;
 }
 
-bool RenderBlock::hasMarginAfterQuirk(const RenderBox* child) const
+bool RenderBlock::hasMarginAfterQuirk(const RenderBox& child) const
 {
     // If the child has the same directionality as we do, then we can just return its
     // margin quirk.
-    if (!child->isWritingModeRoot())
-        return child->isRenderBlock() ? toRenderBlock(child)->hasMarginAfterQuirk() : child->style()->hasMarginAfterQuirk();
+    if (!child.isWritingModeRoot())
+        return is<RenderBlock>(child) ? downcast<RenderBlock>(child).hasMarginAfterQuirk() : child.style().hasMarginAfterQuirk();
     
     // The child has a different directionality. If the child is parallel, then it's just
     // flipped relative to us. We can use the opposite edge.
-    if (child->isHorizontalWritingMode() == isHorizontalWritingMode())
-        return child->isRenderBlock() ? toRenderBlock(child)->hasMarginBeforeQuirk() : child->style()->hasMarginBeforeQuirk();
+    if (child.isHorizontalWritingMode() == isHorizontalWritingMode())
+        return is<RenderBlock>(child) ? downcast<RenderBlock>(child).hasMarginBeforeQuirk() : child.style().hasMarginBeforeQuirk();
     
     // The child is perpendicular to us and box sides are never quirky in html.css, and we don't really care about
     // whether or not authors specified quirky ems, since they're an implementation detail.
     return false;
 }
 
-RenderBlock::MarginValues RenderBlock::marginValuesForChild(RenderBox* child) const
-{
-    LayoutUnit childBeforePositive = 0;
-    LayoutUnit childBeforeNegative = 0;
-    LayoutUnit childAfterPositive = 0;
-    LayoutUnit childAfterNegative = 0;
-
-    LayoutUnit beforeMargin = 0;
-    LayoutUnit afterMargin = 0;
-
-    RenderBlock* childRenderBlock = child->isRenderBlock() ? toRenderBlock(child) : 0;
-    
-    // If the child has the same directionality as we do, then we can just return its
-    // margins in the same direction.
-    if (!child->isWritingModeRoot()) {
-        if (childRenderBlock) {
-            childBeforePositive = childRenderBlock->maxPositiveMarginBefore();
-            childBeforeNegative = childRenderBlock->maxNegativeMarginBefore();
-            childAfterPositive = childRenderBlock->maxPositiveMarginAfter();
-            childAfterNegative = childRenderBlock->maxNegativeMarginAfter();
-        } else {
-            beforeMargin = child->marginBefore();
-            afterMargin = child->marginAfter();
-        }
-    } else if (child->isHorizontalWritingMode() == isHorizontalWritingMode()) {
-        // The child has a different directionality.  If the child is parallel, then it's just
-        // flipped relative to us.  We can use the margins for the opposite edges.
-        if (childRenderBlock) {
-            childBeforePositive = childRenderBlock->maxPositiveMarginAfter();
-            childBeforeNegative = childRenderBlock->maxNegativeMarginAfter();
-            childAfterPositive = childRenderBlock->maxPositiveMarginBefore();
-            childAfterNegative = childRenderBlock->maxNegativeMarginBefore();
-        } else {
-            beforeMargin = child->marginAfter();
-            afterMargin = child->marginBefore();
-        }
-    } else {
-        // The child is perpendicular to us, which means its margins don't collapse but are on the
-        // "logical left/right" sides of the child box.  We can just return the raw margin in this case.
-        beforeMargin = marginBeforeForChild(child);
-        afterMargin = marginAfterForChild(child);
-    }
-
-    // Resolve uncollapsing margins into their positive/negative buckets.
-    if (beforeMargin) {
-        if (beforeMargin > 0)
-            childBeforePositive = beforeMargin;
-        else
-            childBeforeNegative = -beforeMargin;
-    }
-    if (afterMargin) {
-        if (afterMargin > 0)
-            childAfterPositive = afterMargin;
-        else
-            childAfterNegative = -afterMargin;
-    }
-
-    return MarginValues(childBeforePositive, childBeforeNegative, childAfterPositive, childAfterNegative);
-}
-
 const char* RenderBlock::renderName() const
 {
     if (isBody())
         return "RenderBody"; // FIXME: Temporary hack until we know that the regression tests pass.
-    
+
     if (isFloating())
         return "RenderBlock (floating)";
     if (isOutOfFlowPositioned())
         return "RenderBlock (positioned)";
-    if (style() && isAnonymousColumnsBlock())
-        return "RenderBlock (anonymous multi-column)";
-    if (style() && isAnonymousColumnSpanBlock())
-        return "RenderBlock (anonymous multi-column span)";
-    if (style() && isAnonymousBlock())
+    if (isAnonymousBlock())
         return "RenderBlock (anonymous)";
+    if (isAnonymousInlineBlock())
+        return "RenderBlock (anonymous inline-block)";
     // FIXME: Temporary hack while the new generated content system is being implemented.
     if (isPseudoElement())
         return "RenderBlock (generated)";
@@ -7997,238 +3703,65 @@ const char* RenderBlock::renderName() const
         return "RenderBlock (relative positioned)";
     if (isStickyPositioned())
         return "RenderBlock (sticky positioned)";
-    if (style() && isRunIn())
-        return "RenderBlock (run-in)";
     return "RenderBlock";
 }
 
-inline RenderBlock::FloatingObjects::FloatingObjects(const RenderBlock* renderer, bool horizontalWritingMode)
-    : m_placedFloatsTree(UninitializedTree)
-    , m_leftObjectsCount(0)
-    , m_rightObjectsCount(0)
-    , m_horizontalWritingMode(horizontalWritingMode)
-    , m_renderer(renderer)
-{
-}
-
-void RenderBlock::createFloatingObjects()
-{
-    m_floatingObjects = adoptPtr(new FloatingObjects(this, isHorizontalWritingMode()));
-}
-
-inline void RenderBlock::FloatingObjects::clear()
-{
-    m_set.clear();
-    m_placedFloatsTree.clear();
-    m_leftObjectsCount = 0;
-    m_rightObjectsCount = 0;
-}
-
-inline void RenderBlock::FloatingObjects::increaseObjectsCount(FloatingObject::Type type)
-{    
-    if (type == FloatingObject::FloatLeft)
-        m_leftObjectsCount++;
-    else 
-        m_rightObjectsCount++;
-}
-
-inline void RenderBlock::FloatingObjects::decreaseObjectsCount(FloatingObject::Type type)
-{
-    if (type == FloatingObject::FloatLeft)
-        m_leftObjectsCount--;
-    else
-        m_rightObjectsCount--;
-}
-
-inline RenderBlock::FloatingObjectInterval RenderBlock::FloatingObjects::intervalForFloatingObject(FloatingObject* floatingObject)
-{
-    if (m_horizontalWritingMode)
-        return RenderBlock::FloatingObjectInterval(floatingObject->frameRect().y(), floatingObject->frameRect().maxY(), floatingObject);
-    return RenderBlock::FloatingObjectInterval(floatingObject->frameRect().x(), floatingObject->frameRect().maxX(), floatingObject);
-}
-
-void RenderBlock::FloatingObjects::addPlacedObject(FloatingObject* floatingObject)
-{
-    ASSERT(!floatingObject->isInPlacedTree());
-
-    floatingObject->setIsPlaced(true);
-    if (m_placedFloatsTree.isInitialized())
-        m_placedFloatsTree.add(intervalForFloatingObject(floatingObject));
-
-#ifndef NDEBUG
-    floatingObject->setIsInPlacedTree(true);      
-#endif
-}
-
-void RenderBlock::FloatingObjects::removePlacedObject(FloatingObject* floatingObject)
-{
-    ASSERT(floatingObject->isPlaced() && floatingObject->isInPlacedTree());
-
-    if (m_placedFloatsTree.isInitialized()) {
-        bool removed = m_placedFloatsTree.remove(intervalForFloatingObject(floatingObject));
-        ASSERT_UNUSED(removed, removed);
-    }
-    
-    floatingObject->setIsPlaced(false);
-#ifndef NDEBUG
-    floatingObject->setIsInPlacedTree(false);
-#endif
-}
-
-inline void RenderBlock::FloatingObjects::add(FloatingObject* floatingObject)
-{
-    increaseObjectsCount(floatingObject->type());
-    m_set.add(floatingObject);
-    if (floatingObject->isPlaced())
-        addPlacedObject(floatingObject);
-}
-
-inline void RenderBlock::FloatingObjects::remove(FloatingObject* floatingObject)
-{
-    decreaseObjectsCount(floatingObject->type());
-    m_set.remove(floatingObject);
-    ASSERT(floatingObject->isPlaced() || !floatingObject->isInPlacedTree());
-    if (floatingObject->isPlaced())
-        removePlacedObject(floatingObject);
-}
-
-void RenderBlock::FloatingObjects::computePlacedFloatsTree()
+TextRun RenderBlock::constructTextRun(RenderObject* context, const FontCascade& font, StringView stringView, const RenderStyle& style, ExpansionBehavior expansion, TextRunFlags flags)
 {
-    ASSERT(!m_placedFloatsTree.isInitialized());
-    if (m_set.isEmpty())
-        return;
-    m_placedFloatsTree.initIfNeeded(m_renderer->view()->intervalArena());
-    FloatingObjectSetIterator it = m_set.begin();
-    FloatingObjectSetIterator end = m_set.end();
-    for (; it != end; ++it) {
-        FloatingObject* floatingObject = *it;
-        if (floatingObject->isPlaced())
-            m_placedFloatsTree.add(intervalForFloatingObject(floatingObject));
-    }
-}
-
-template <typename CharacterType>
-static inline TextRun constructTextRunInternal(RenderObject* context, const Font& font, const CharacterType* characters, int length, RenderStyle* style, TextRun::ExpansionBehavior expansion)
-{
-    ASSERT(style);
-
-    TextDirection textDirection = LTR;
-    bool directionalOverride = style->rtlOrdering() == VisualOrder;
-
-    TextRun run(characters, length, 0, 0, expansion, textDirection, directionalOverride);
-    if (textRunNeedsRenderingContext(font))
-        run.setRenderingContext(SVGTextRunRenderingContext::create(context));
-
-    return run;
-}
-
-template <typename CharacterType>
-static inline TextRun constructTextRunInternal(RenderObject* context, const Font& font, const CharacterType* characters, int length, RenderStyle* style, TextRun::ExpansionBehavior expansion, TextRunFlags flags)
-{
-    ASSERT(style);
-
     TextDirection textDirection = LTR;
-    bool directionalOverride = style->rtlOrdering() == VisualOrder;
+    bool directionalOverride = style.rtlOrdering() == VisualOrder;
     if (flags != DefaultTextRunFlags) {
         if (flags & RespectDirection)
-            textDirection = style->direction();
+            textDirection = style.direction();
         if (flags & RespectDirectionOverride)
-            directionalOverride |= isOverride(style->unicodeBidi());
+            directionalOverride |= isOverride(style.unicodeBidi());
+    }
+    TextRun run(stringView, 0, 0, expansion, textDirection, directionalOverride);
+    if (font.primaryFont().isSVGFont()) {
+        ASSERT(context); // FIXME: Thread a RenderObject& to this point so we don't have to dereference anything.
+        run.setRenderingContext(SVGTextRunRenderingContext::create(*context));
     }
-    TextRun run(characters, length, 0, 0, expansion, textDirection, directionalOverride);
-    if (textRunNeedsRenderingContext(font))
-        run.setRenderingContext(SVGTextRunRenderingContext::create(context));
 
     return run;
 }
 
-#if ENABLE(8BIT_TEXTRUN)
-TextRun RenderBlock::constructTextRun(RenderObject* context, const Font& font, const LChar* characters, int length, RenderStyle* style, TextRun::ExpansionBehavior expansion)
+TextRun RenderBlock::constructTextRun(RenderObject* context, const FontCascade& font, const String& string, const RenderStyle& style, ExpansionBehavior expansion, TextRunFlags flags)
 {
-    return constructTextRunInternal(context, font, characters, length, style, expansion);
+    return constructTextRun(context, font, StringView(string), style, expansion, flags);
 }
-#endif
 
-TextRun RenderBlock::constructTextRun(RenderObject* context, const Font& font, const UChar* characters, int length, RenderStyle* style, TextRun::ExpansionBehavior expansion)
+TextRun RenderBlock::constructTextRun(RenderObject* context, const FontCascade& font, const RenderText* text, const RenderStyle& style, ExpansionBehavior expansion)
 {
-    return constructTextRunInternal(context, font, characters, length, style, expansion);
+    return constructTextRun(context, font, text->stringView(), style, expansion);
 }
 
-TextRun RenderBlock::constructTextRun(RenderObject* context, const Font& font, const RenderText* text, RenderStyle* style, TextRun::ExpansionBehavior expansion)
+TextRun RenderBlock::constructTextRun(RenderObject* context, const FontCascade& font, const RenderText* text, unsigned offset, unsigned length, const RenderStyle& style, ExpansionBehavior expansion)
 {
-#if ENABLE(8BIT_TEXTRUN)
-    if (text->is8Bit())
-        return constructTextRunInternal(context, font, text->characters8(), text->textLength(), style, expansion);
-    return constructTextRunInternal(context, font, text->characters16(), text->textLength(), style, expansion);
-#else
-    return constructTextRunInternal(context, font, text->characters(), text->textLength(), style, expansion);
-#endif
+    unsigned stop = offset + length;
+    ASSERT(stop <= text->textLength());
+    return constructTextRun(context, font, text->stringView(offset, stop), style, expansion);
 }
 
-TextRun RenderBlock::constructTextRun(RenderObject* context, const Font& font, const RenderText* text, unsigned offset, unsigned length, RenderStyle* style, TextRun::ExpansionBehavior expansion)
+TextRun RenderBlock::constructTextRun(RenderObject* context, const FontCascade& font, const LChar* characters, int length, const RenderStyle& style, ExpansionBehavior expansion)
 {
-    ASSERT(offset + length <= text->textLength());
-#if ENABLE(8BIT_TEXTRUN)
-    if (text->is8Bit())
-        return constructTextRunInternal(context, font, text->characters8() + offset, length, style, expansion);
-    return constructTextRunInternal(context, font, text->characters16() + offset, length, style, expansion);
-#else
-    return constructTextRunInternal(context, font, text->characters() + offset, length, style, expansion);
-#endif
+    return constructTextRun(context, font, StringView(characters, length), style, expansion);
 }
 
-TextRun RenderBlock::constructTextRun(RenderObject* context, const Font& font, const String& string, RenderStyle* style, TextRun::ExpansionBehavior expansion, TextRunFlags flags)
+TextRun RenderBlock::constructTextRun(RenderObject* context, const FontCascade& font, const UChar* characters, int length, const RenderStyle& style, ExpansionBehavior expansion)
 {
-    unsigned length = string.length();
-
-#if ENABLE(8BIT_TEXTRUN)
-    if (length && string.is8Bit())
-        return constructTextRunInternal(context, font, string.characters8(), length, style, expansion, flags);
-    return constructTextRunInternal(context, font, string.characters(), length, style, expansion, flags);
-#else
-    return constructTextRunInternal(context, font, string.characters(), length, style, expansion, flags);
-#endif
+    return constructTextRun(context, font, StringView(characters, length), style, expansion);
 }
 
 RenderBlock* RenderBlock::createAnonymousWithParentRendererAndDisplay(const RenderObject* parent, EDisplay display)
 {
     // FIXME: Do we need to convert all our inline displays to block-type in the anonymous logic ?
-    EDisplay newDisplay;
-    RenderBlock* newBox = 0;
-    if (display == BOX || display == INLINE_BOX) {
-        // FIXME: Remove this case once we have eliminated all internal users of old flexbox
-        newBox = RenderDeprecatedFlexibleBox::createAnonymous(parent->document());
-        newDisplay = BOX;
-    } else if (display == FLEX || display == INLINE_FLEX) {
-        newBox = RenderFlexibleBox::createAnonymous(parent->document());
-        newDisplay = FLEX;
-    } else {
-        newBox = RenderBlock::createAnonymous(parent->document());
-        newDisplay = BLOCK;
-    }
-
-    RefPtr<RenderStyle> newStyle = RenderStyle::createAnonymousStyleWithDisplay(parent->style(), newDisplay);
-    newBox->setStyle(newStyle.release());
-    return newBox;
-}
-
-RenderBlock* RenderBlock::createAnonymousColumnsWithParentRenderer(const RenderObject* parent)
-{
-    RefPtr<RenderStyle> newStyle = RenderStyle::createAnonymousStyleWithDisplay(parent->style(), BLOCK);
-    newStyle->inheritColumnPropertiesFrom(parent->style());
-
-    RenderBlock* newBox = RenderBlock::createAnonymous(parent->document());
-    newBox->setStyle(newStyle.release());
-    return newBox;
-}
-
-RenderBlock* RenderBlock::createAnonymousColumnSpanWithParentRenderer(const RenderObject* parent)
-{
-    RefPtr<RenderStyle> newStyle = RenderStyle::createAnonymousStyleWithDisplay(parent->style(), BLOCK);
-    newStyle->setColumnSpan(ColumnSpanAll);
+    RenderBlock* newBox;
+    if (display == FLEX || display == INLINE_FLEX)
+        newBox = new RenderFlexibleBox(parent->document(), RenderStyle::createAnonymousStyleWithDisplay(&parent->style(), FLEX));
+    else
+        newBox = new RenderBlockFlow(parent->document(), RenderStyle::createAnonymousStyleWithDisplay(&parent->style(), BLOCK));
 
-    RenderBlock* newBox = RenderBlock::createAnonymous(parent->document());
-    newBox->setStyle(newStyle.release());
+    newBox->initializeStyle();
     return newBox;
 }
 
@@ -8238,31 +3771,14 @@ void RenderBlock::checkPositionedObjectsNeedLayout()
     if (!gPositionedDescendantsMap)
         return;
 
-    if (TrackedRendererListHashSet* positionedDescendantSet = positionedObjects()) {
-        TrackedRendererListHashSet::const_iterator end = positionedDescendantSet->end();
-        for (TrackedRendererListHashSet::const_iterator it = positionedDescendantSet->begin(); it != end; ++it) {
-            RenderBox* currBox = *it;
-            ASSERT(!currBox->needsLayout());
-        }
-    }
-}
-
-void RenderBlock::showLineTreeAndMark(const InlineBox* markedBox1, const char* markedLabel1, const InlineBox* markedBox2, const char* markedLabel2, const RenderObject* obj) const
-{
-    showRenderObject();
-    for (const RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox())
-        root->showLineTreeAndMark(markedBox1, markedLabel1, markedBox2, markedLabel2, obj, 1);
-}
-
-// These helpers are only used by the PODIntervalTree for debugging purposes.
-String ValueToString<int>::string(const int value)
-{
-    return String::number(value);
-}
+    TrackedRendererListHashSet* positionedDescendantSet = positionedObjects();
+    if (!positionedDescendantSet)
+        return;
 
-String ValueToString<RenderBlock::FloatingObject*>::string(const RenderBlock::FloatingObject* floatingObject)
-{
-    return String::format("%p (%ix%i %ix%i)", floatingObject, floatingObject->frameRect().x().toInt(), floatingObject->frameRect().y().toInt(), floatingObject->frameRect().maxX().toInt(), floatingObject->frameRect().maxY().toInt());
+    for (auto it = positionedDescendantSet->begin(), end = positionedDescendantSet->end(); it != end; ++it) {
+        RenderBox* currBox = *it;
+        ASSERT(!currBox->needsLayout());
+    }
 }
 
 #endif
-- 
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