Imported WebKit commit 2ea9d364d0f6efa8fa64acf19f451504c59be0e4 (http://svn.webkit.org/repository/webkit/trunk@104285)

1 files changed, 7040 insertions, 0 deletions

diff --git a/Source/WebCore/rendering/RenderBlock.cpp b/Source/WebCore/rendering/RenderBlock.cpp
new file mode 100755
index 000000000..f5a33f4ce
--- /dev/null
+++ b/Source/WebCore/rendering/RenderBlock.cpp
@@ -0,0 +1,7040 @@
+/*
+ * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
+ *           (C) 1999 Antti Koivisto (koivisto@kde.org)
+ *           (C) 2007 David Smith (catfish.man@gmail.com)
+ * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
+ * Copyright (C) Research In Motion Limited 2010. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public License
+ * along with this library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include "config.h"
+#include "RenderBlock.h"
+
+#include "ColumnInfo.h"
+#include "Document.h"
+#include "Element.h"
+#include "FloatQuad.h"
+#include "Frame.h"
+#include "FrameSelection.h"
+#include "FrameView.h"
+#include "GraphicsContext.h"
+#include "HTMLFormElement.h"
+#include "HTMLNames.h"
+#include "HitTestResult.h"
+#include "InlineIterator.h"
+#include "InlineTextBox.h"
+#include "LayoutRepainter.h"
+#include "PODFreeListArena.h"
+#include "Page.h"
+#include "PaintInfo.h"
+#include "RenderBoxRegionInfo.h"
+#include "RenderCombineText.h"
+#include "RenderDeprecatedFlexibleBox.h"
+#include "RenderFlowThread.h"
+#include "RenderImage.h"
+#include "RenderInline.h"
+#include "RenderLayer.h"
+#include "RenderMarquee.h"
+#include "RenderRegion.h"
+#include "RenderReplica.h"
+#include "RenderTableCell.h"
+#include "RenderTextFragment.h"
+#include "RenderTheme.h"
+#include "RenderView.h"
+#include "Settings.h"
+#include "SVGTextRunRenderingContext.h"
+#include "TransformState.h"
+#include <wtf/StdLibExtras.h>
+
+using namespace std;
+using namespace WTF;
+using namespace Unicode;
+
+namespace WebCore {
+
+using namespace HTMLNames;
+
+typedef WTF::HashMap<const RenderBox*, ColumnInfo*> ColumnInfoMap;
+static ColumnInfoMap* gColumnInfoMap = 0;
+
+typedef WTF::HashMap<const RenderBlock*, HashSet<RenderBox*>*> PercentHeightDescendantsMap;
+static PercentHeightDescendantsMap* gPercentHeightDescendantsMap = 0;
+
+typedef WTF::HashMap<const RenderBox*, HashSet<RenderBlock*>*> PercentHeightContainerMap;
+static PercentHeightContainerMap* gPercentHeightContainerMap = 0;
+    
+typedef WTF::HashMap<RenderBlock*, ListHashSet<RenderInline*>*> ContinuationOutlineTableMap;
+
+typedef WTF::HashSet<RenderBlock*> DelayedUpdateScrollInfoSet;
+static int gDelayUpdateScrollInfo = 0;
+static DelayedUpdateScrollInfoSet* gDelayedUpdateScrollInfoSet = 0;
+
+bool RenderBlock::s_canPropagateFloatIntoSibling = false;
+
+// 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_marginBeforeQuirk(false)
+    , m_marginAfterQuirk(false)
+    , m_determinedMarginBeforeQuirk(false)
+{
+    // Whether or not we can collapse our own margins with our children.  We don't do this
+    // if we had any border/padding (obviously), if we're the root or HTML elements, or if
+    // we're positioned, floating, a table cell.
+    m_canCollapseWithChildren = !block->isRenderView() && !block->isRoot() && !block->isPositioned()
+        && !block->isFloating() && !block->isTableCell() && !block->hasOverflowClip() && !block->isInlineBlockOrInlineTable()
+        && !block->isWritingModeRoot() && block->style()->hasAutoColumnCount() && block->style()->hasAutoColumnWidth()
+        && !block->style()->columnSpan();
+
+    m_canCollapseMarginBeforeWithChildren = m_canCollapseWithChildren && (beforeBorderPadding == 0) && block->style()->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) &&
+        (block->style()->logicalHeight().isAuto() && block->style()->logicalHeight().value() == 0) && block->style()->marginAfterCollapse() != MSEPARATE;
+    
+    m_quirkContainer = block->isTableCell() || block->isBody() || block->style()->marginBeforeCollapse() == MDISCARD || 
+        block->style()->marginAfterCollapse() == MDISCARD;
+
+    m_positiveMargin = m_canCollapseMarginBeforeWithChildren ? block->maxPositiveMarginBefore() : 0;
+    m_negativeMargin = m_canCollapseMarginBeforeWithChildren ? block->maxNegativeMarginBefore() : 0;
+}
+
+// -------------------------------------------------------------------------------------------------------
+
+RenderBlock::RenderBlock(Node* node)
+      : RenderBox(node)
+      , m_lineHeight(-1)
+      , m_beingDestroyed(false)
+      , m_hasPositionedFloats(false)
+{
+    setChildrenInline(true);
+}
+
+RenderBlock::~RenderBlock()
+{
+    if (m_floatingObjects)
+        deleteAllValues(m_floatingObjects->set());
+    
+    if (hasColumns())
+        delete gColumnInfoMap->take(this);
+
+    if (gPercentHeightDescendantsMap) {
+        if (HashSet<RenderBox*>* descendantSet = gPercentHeightDescendantsMap->take(this)) {
+            HashSet<RenderBox*>::iterator end = descendantSet->end();
+            for (HashSet<RenderBox*>::iterator descendant = descendantSet->begin(); descendant != end; ++descendant) {
+                HashSet<RenderBlock*>* containerSet = gPercentHeightContainerMap->get(*descendant);
+                ASSERT(containerSet);
+                if (!containerSet)
+                    continue;
+                ASSERT(containerSet->contains(this));
+                containerSet->remove(this);
+                if (containerSet->isEmpty()) {
+                    gPercentHeightContainerMap->remove(*descendant);
+                    delete containerSet;
+                }
+            }
+            delete descendantSet;
+        }
+    }
+}
+
+void RenderBlock::willBeDestroyed()
+{
+    // Mark as being destroyed to avoid trouble with merges in removeChild().
+    m_beingDestroyed = true;
+
+    // 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);
+    }
+
+    m_lineBoxes.deleteLineBoxes(renderArena());
+
+    if (UNLIKELY(gDelayedUpdateScrollInfoSet != 0))
+        gDelayedUpdateScrollInfoSet->remove(this);
+
+    RenderBox::willBeDestroyed();
+}
+
+void RenderBlock::styleWillChange(StyleDifference diff, const RenderStyle* newStyle)
+{
+    s_canPropagateFloatIntoSibling = style() ? !isFloatingOrPositioned() && !avoidsFloats() : false;
+
+    setReplaced(newStyle->isDisplayInlineType());
+    
+    if (style() && parent() && diff == StyleDifferenceLayout && style()->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);
+        else if (style()->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();
+            }
+            
+            if (cb->isRenderBlock())
+                toRenderBlock(cb)->removePositionedObjects(this);
+        }
+
+        if (containsFloats() && !isFloating() && !isPositioned() && (newStyle->position() == AbsolutePosition || newStyle->position() == FixedPosition))
+            markAllDescendantsWithFloatsForLayout();
+    }
+
+    RenderBox::styleWillChange(diff, newStyle);
+}
+
+void RenderBlock::styleDidChange(StyleDifference diff, const RenderStyle* oldStyle)
+{
+    RenderBox::styleDidChange(diff, oldStyle);
+
+    if (!isAnonymousBlock()) {
+        // Ensure that all of our continuation blocks pick up the new style.
+        for (RenderBlock* currCont = blockElementContinuation(); currCont; currCont = currCont->blockElementContinuation()) {
+            RenderBoxModelObject* nextCont = currCont->continuation();
+            currCont->setContinuation(0);
+            currCont->setStyle(style());
+            currCont->setContinuation(nextCont);
+        }
+    }
+
+    propagateStyleToAnonymousChildren(true);    
+    m_lineHeight = -1;
+
+    // Update pseudos for :before and :after now.
+    if (!isAnonymous() && document()->usesBeforeAfterRules() && canHaveChildren()) {
+        updateBeforeAfterContent(BEFORE);
+        updateBeforeAfterContent(AFTER);
+    }
+
+    // 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 = !isFloatingOrPositioned() && !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();
+    }
+}
+
+void RenderBlock::updateBeforeAfterContent(PseudoId pseudoId)
+{
+    // If this is an anonymous wrapper, then the parent applies its own pseudo-element style to it.
+    if (parent() && parent()->createsAnonymousWrapper())
+        return;
+    children()->updateBeforeAfterContent(this, pseudoId);
+}
+
+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)
+                return last;
+            return curr;
+        }
+
+        nextToLast = last;
+        last = curr;
+        curr = toRenderBlock(curr->continuation());
+    }
+
+    if (!beforeChild && !last->firstChild())
+        return nextToLast;
+    return last;
+}
+
+void RenderBlock::addChildToContinuation(RenderObject* newChild, RenderObject* beforeChild)
+{
+    RenderBlock* flow = continuationBefore(beforeChild);
+    ASSERT(!beforeChild || beforeChild->parent()->isAnonymousColumnSpanBlock() || beforeChild->parent()->isRenderBlock());
+    RenderBoxModelObject* beforeChildParent = 0;
+    if (beforeChild)
+        beforeChildParent = toRenderBoxModelObject(beforeChild->parent());
+    else {
+        RenderBoxModelObject* cont = flow->continuation();
+        if (cont)
+            beforeChildParent = cont;
+        else
+            beforeChildParent = flow;
+    }
+
+    if (newChild->isFloatingOrPositioned()) {
+        beforeChildParent->addChildIgnoringContinuation(newChild, beforeChild);
+        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();
+
+    if (flow == beforeChildParent) {
+        flow->addChildIgnoringContinuation(newChild, beforeChild);
+        return;
+    }
+    
+    // The goal here is to match up if we can, so that we can coalesce and create the
+    // minimal # of continuations needed for the inline.
+    if (childIsNormal == bcpIsNormal) {
+        beforeChildParent->addChildIgnoringContinuation(newChild, beforeChild);
+        return;
+    }
+    if (flowIsNormal == childIsNormal) {
+        flow->addChildIgnoringContinuation(newChild, 0); // Just treat like an append.
+        return;
+    }
+    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 = toRenderBlock(beforeChild && beforeChild->parent()->isRenderBlock() ? beforeChild->parent() : lastChild());
+    
+    // If the new child is floating or positioned it can just go in that block.
+    if (newChild->isFloatingOrPositioned()) {
+        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 = splitAnonymousBlocksAroundChild(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)
+{
+    for (RenderObject* curr = this; curr; curr = curr->parent()) {
+        if (!curr->isRenderBlock() || curr->isFloatingOrPositioned() || curr->isTableCell() || curr->isRoot() || curr->isRenderView() || curr->hasOverflowClip()
+            || curr->isInlineBlockOrInlineTable())
+            return 0;
+        
+        RenderBlock* currBlock = toRenderBlock(curr);
+        if (currBlock->style()->specifiesColumns() && (allowAnonymousColumnBlock || !currBlock->isAnonymousColumnsBlock()))
+            return currBlock;
+            
+        if (currBlock->isAnonymousColumnSpanBlock())
+            return 0;
+    }
+    return 0;
+}
+
+RenderBlock* RenderBlock::clone() const
+{
+    RenderBlock* cloneBlock;
+    if (isAnonymousBlock())
+        cloneBlock = createAnonymousBlock();
+    else {
+        cloneBlock = new (renderArena()) RenderBlock(node());
+        cloneBlock->setStyle(style());
+    }
+    cloneBlock->setChildrenInline(childrenInline());
+    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);
+
+    // Now take all of the children from beforeChild to the end and remove
+    // them from |this| and place them in the clone.
+    if (!beforeChild && isAfterContent(lastChild()))
+        beforeChild = lastChild();
+    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;
+    
+    while (curr && curr != fromBlock) {
+        ASSERT(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->children()->appendChildNode(cloneBlock, cloneChild);
+
+        // 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);
+        }
+
+        // Someone may have indirectly caused a <q> to split.  When this happens, the :after content
+        // has to move into the inline continuation.  Call updateBeforeAfterContent to ensure that the inline's :after
+        // content gets properly destroyed.
+        if (document()->usesBeforeAfterRules())
+            blockCurr->children()->updateBeforeAfterContent(blockCurr, AFTER);
+
+        // 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, currChild->nextSibling(), 0, true);
+
+        // Keep walking up the chain.
+        currChild = curr;
+        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, currChild->nextSibling(), 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);
+        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();
+}
+
+RenderObject* RenderBlock::splitAnonymousBlocksAroundChild(RenderObject* beforeChild)
+{
+    while (beforeChild->parent() != this) {
+        RenderBlock* blockToSplit = toRenderBlock(beforeChild->parent());
+        if (blockToSplit->firstChild() != beforeChild) {
+            // We have to split the parentBlock into two blocks.
+            RenderBlock* post = createAnonymousBlockWithSameTypeAs(blockToSplit);
+            post->setChildrenInline(blockToSplit->childrenInline());
+            RenderBlock* parentBlock = toRenderBlock(blockToSplit->parent());
+            parentBlock->children()->insertChildNode(parentBlock, post, blockToSplit->nextSibling());
+            blockToSplit->moveChildrenTo(post, beforeChild, 0, blockToSplit->hasLayer());
+            post->setNeedsLayoutAndPrefWidthsRecalc();
+            blockToSplit->setNeedsLayoutAndPrefWidthsRecalc();
+            beforeChild = post;
+        } else
+            beforeChild = blockToSplit;
+    }
+    return beforeChild;
+}
+
+void RenderBlock::makeChildrenAnonymousColumnBlocks(RenderObject* beforeChild, RenderBlock* newBlockBox, RenderObject* newChild)
+{
+    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 = splitAnonymousBlocksAroundChild(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->isFloatingOrPositioned()
+        && !newChild->isInline() && !isAnonymousColumnSpanBlock()) {
+        if (style()->specifiesColumns())
+            columnsBlockAncestor = this;
+        else if (!isInline() && parent() && parent()->isRenderBlock()) {
+            columnsBlockAncestor = toRenderBlock(parent())->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;
+}
+
+void RenderBlock::addChildIgnoringAnonymousColumnBlocks(RenderObject* newChild, RenderObject* beforeChild)
+{
+    // Make sure we don't append things after :after-generated content if we have it.
+    if (!beforeChild)
+        beforeChild = afterPseudoElementRenderer();
+
+    // 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.
+    if (beforeChild && beforeChild->parent() != this) {
+        RenderObject* beforeChildAnonymousContainer = anonymousContainer(beforeChild);
+        ASSERT(beforeChildAnonymousContainer);
+        ASSERT(beforeChildAnonymousContainer->isAnonymous());
+
+        if (beforeChildAnonymousContainer->isAnonymousBlock()) {
+            // Insert the child into the anonymous block box instead of here.
+            if (newChild->isInline() || beforeChild->parent()->firstChild() != beforeChild)
+                beforeChild->parent()->addChild(newChild, beforeChild);
+            else
+                addChild(newChild, beforeChild->parent());
+            return;
+        }
+
+        ASSERT(beforeChildAnonymousContainer->isTable());
+        if ((newChild->isTableCol() && newChild->style()->display() == TABLE_COLUMN_GROUP)
+                || (newChild->isTableCaption())
+                || newChild->isTableSection()
+                || newChild->isTableRow()
+                || newChild->isTableCell()) {
+            // Insert into the anonymous table.
+            beforeChildAnonymousContainer->addChild(newChild, beforeChild);
+            return;
+        }
+
+        // Go on to insert before the anonymous table.
+        beforeChild = beforeChildAnonymousContainer;
+    }
+
+    // Check for a spanning element in columns.
+    RenderBlock* columnsBlockAncestor = columnsBlockForSpanningElement(newChild);
+    if (columnsBlockAncestor) {
+        // We are placing a column-span element inside a block. 
+        RenderBlock* newBox = createAnonymousColumnSpanBlock();
+        
+        if (columnsBlockAncestor != this) {
+            // 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();
+            setContinuation(newBox);
+
+            // Someone may have put a <p> inside a <q>, causing a split.  When this happens, the :after content
+            // has to move into the inline continuation.  Call updateBeforeAfterContent to ensure that our :after
+            // content gets properly destroyed.
+            bool isLastChild = (beforeChild == lastChild());
+            if (document()->usesBeforeAfterRules())
+                children()->updateBeforeAfterContent(this, AFTER);
+            if (isLastChild && beforeChild != lastChild())
+                beforeChild = 0; // We destroyed the last child, so now we need to update our insertion
+                                 // point to be 0.  It's just a straight append now.
+
+            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;
+    }
+
+    bool madeBoxesNonInline = false;
+
+    // A block has to either have all of its children inline, or all of its children as blocks.
+    // So, if our children are currently inline and a block child has to be inserted, we move all our
+    // inline children into anonymous block boxes.
+    if (childrenInline() && !newChild->isInline() && !newChild->isFloatingOrPositioned()) {
+        // This is a block with inline content. Wrap the inline content in anonymous blocks.
+        makeChildrenNonInline(beforeChild);
+        madeBoxesNonInline = true;
+
+        if (beforeChild && beforeChild->parent() != this) {
+            beforeChild = beforeChild->parent();
+            ASSERT(beforeChild->isAnonymousBlock());
+            ASSERT(beforeChild->parent() == this);
+        }
+    } else if (!childrenInline() && (newChild->isFloatingOrPositioned() || newChild->isInline())) {
+        // If we're inserting an inline child but all of our children are blocks, then we have to make sure
+        // it is put into an anomyous block box. We try to use an existing anonymous box if possible, otherwise
+        // a new one is created and inserted into our list of children in the appropriate position.
+        RenderObject* afterChild = beforeChild ? beforeChild->previousSibling() : lastChild();
+
+        if (afterChild && afterChild->isAnonymousBlock()) {
+            afterChild->addChild(newChild);
+            return;
+        }
+
+        if (newChild->isInline()) {
+            // No suitable existing anonymous box - create a new one.
+            RenderBlock* newBox = createAnonymousBlock();
+            RenderBox::addChild(newBox, beforeChild);
+            newBox->addChild(newChild);
+            return;
+        }
+    }
+
+    RenderBox::addChild(newChild, beforeChild);
+
+    if (madeBoxesNonInline && parent() && isAnonymousBlock() && parent()->isRenderBlock())
+        toRenderBlock(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)
+{
+    // Beginning at |start| we find the largest contiguous run of inlines that
+    // we can.  We denote the run with start and end points, |inlineRunStart|
+    // and |inlineRunEnd|.  Note that these two values may be the same if
+    // we encounter only one inline.
+    //
+    // We skip any non-inlines we encounter as long as we haven't found any
+    // inlines yet.
+    //
+    // |boundary| indicates a non-inclusive boundary point.  Regardless of whether |boundary|
+    // is inline or not, we will not include it in a run with inlines before it.  It's as though we encountered
+    // a non-inline.
+    
+    // Start by skipping as many non-inlines as we can.
+    RenderObject * curr = start;
+    bool sawInline;
+    do {
+        while (curr && !(curr->isInline() || curr->isFloatingOrPositioned()))
+            curr = curr->nextSibling();
+        
+        inlineRunStart = inlineRunEnd = curr;
+        
+        if (!curr)
+            return; // No more inline children to be found.
+        
+        sawInline = curr->isInline();
+        
+        curr = curr->nextSibling();
+        while (curr && (curr->isInline() || curr->isFloatingOrPositioned()) && (curr != boundary)) {
+            inlineRunEnd = curr;
+            if (curr->isInline())
+                sawInline = true;
+            curr = curr->nextSibling();
+        }
+    } while (!sawInline);
+}
+
+void RenderBlock::deleteLineBoxTree()
+{
+    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());
+}
+
+RootInlineBox* RenderBlock::createRootInlineBox() 
+{
+    return new (renderArena()) RootInlineBox(this);
+}
+
+RootInlineBox* RenderBlock::createAndAppendRootInlineBox()
+{
+    RootInlineBox* rootBox = createRootInlineBox();
+    m_lineBoxes.appendLineBox(rootBox);
+    return rootBox;
+}
+
+void RenderBlock::moveChildTo(RenderBlock* to, RenderObject* child, RenderObject* beforeChild, bool fullRemoveInsert)
+{
+    ASSERT(this == child->parent());
+    ASSERT(!beforeChild || to == beforeChild->parent());
+    to->children()->insertChildNode(to, children()->removeChildNode(this, child, fullRemoveInsert), beforeChild, fullRemoveInsert);
+}
+
+void RenderBlock::moveChildrenTo(RenderBlock* to, RenderObject* startChild, RenderObject* endChild, RenderObject* beforeChild, bool fullRemoveInsert)
+{
+    ASSERT(!beforeChild || to == beforeChild->parent());
+    RenderObject* nextChild = startChild;
+    while (nextChild && nextChild != endChild) {
+        RenderObject* child = nextChild;
+        nextChild = child->nextSibling();
+        to->children()->insertChildNode(to, children()->removeChildNode(this, child, fullRemoveInsert), beforeChild, fullRemoveInsert);
+        if (child == endChild)
+            return;
+    }
+}
+
+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
+    // blocks.  If |insertionPoint| is defined, then it represents the insertion point for
+    // the new block child that is causing us to have to wrap all the inlines.  This
+    // means that we cannot coalesce inlines before |insertionPoint| with inlines following
+    // |insertionPoint|, because the new child is going to be inserted in between the inlines,
+    // splitting them.
+    ASSERT(isInlineBlockOrInlineTable() || !isInline());
+    ASSERT(!insertionPoint || insertionPoint->parent() == this);
+
+    setChildrenInline(false);
+
+    RenderObject *child = firstChild();
+    if (!child)
+        return;
+
+    deleteLineBoxTree();
+
+    while (child) {
+        RenderObject *inlineRunStart, *inlineRunEnd;
+        getInlineRun(child, insertionPoint, inlineRunStart, inlineRunEnd);
+
+        if (!inlineRunStart)
+            break;
+
+        child = inlineRunEnd->nextSibling();
+
+        RenderBlock* block = createAnonymousBlock();
+        children()->insertChildNode(this, block, inlineRunStart);
+        moveChildrenTo(block, inlineRunStart, child);
+    }
+
+#ifndef NDEBUG
+    for (RenderObject *c = firstChild(); c; c = c->nextSibling())
+        ASSERT(!c->isInline());
+#endif
+
+    repaint();
+}
+
+void RenderBlock::removeLeftoverAnonymousBlock(RenderBlock* child)
+{
+    ASSERT(child->isAnonymousBlock());
+    ASSERT(!child->childrenInline());
+    
+    if (child->continuation() || (child->firstChild() && (child->isAnonymousColumnSpanBlock() || child->isAnonymousColumnsBlock())))
+        return;
+    
+    RenderObject* firstAnChild = child->m_children.firstChild();
+    RenderObject* lastAnChild = child->m_children.lastChild();
+    if (firstAnChild) {
+        RenderObject* o = firstAnChild;
+        while (o) {
+            o->setParent(this);
+            o = o->nextSibling();
+        }
+        firstAnChild->setPreviousSibling(child->previousSibling());
+        lastAnChild->setNextSibling(child->nextSibling());
+        if (child->previousSibling())
+            child->previousSibling()->setNextSibling(firstAnChild);
+        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);
+    } else {
+        if (child == m_children.firstChild())
+            m_children.setFirstChild(child->nextSibling());
+        if (child == m_children.lastChild())
+            m_children.setLastChild(child->previousSibling());
+
+        if (child->previousSibling())
+            child->previousSibling()->setNextSibling(child->nextSibling());
+        if (child->nextSibling())
+            child->nextSibling()->setPreviousSibling(child->previousSibling());
+    }
+    child->setParent(0);
+    child->setPreviousSibling(0);
+    child->setNextSibling(0);
+    
+    child->children()->setFirstChild(0);
+    child->m_next = 0;
+
+    child->destroy();
+}
+
+static bool canMergeContiguousAnonymousBlocks(RenderObject* oldChild, RenderObject* prev, RenderObject* next)
+{
+    if (oldChild->documentBeingDestroyed() || oldChild->isInline() || oldChild->virtualContinuation())
+        return false;
+
+#if ENABLE(DETAILS)
+    if (oldChild->parent() && oldChild->parent()->isDetails())
+        return false;
+#endif
+
+    if ((prev && (!prev->isAnonymousBlock() || toRenderBlock(prev)->continuation() || toRenderBlock(prev)->beingDestroyed()))
+        || (next && (!next->isAnonymousBlock() || toRenderBlock(next)->continuation() || toRenderBlock(next)->beingDestroyed())))
+        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())
+        return false;
+
+    if ((prev && (prev->isRubyRun() || prev->isRubyBase()))
+        || (next && (next->isRubyRun() || next->isRubyBase())))
+        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();
+}
+
+void RenderBlock::removeChild(RenderObject* oldChild)
+{
+    // 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();
+    bool canMergeAnonymousBlocks = canMergeContiguousAnonymousBlocks(oldChild, prev, next);
+    if (canMergeAnonymousBlocks && prev && next) {
+        prev->setNeedsLayoutAndPrefWidthsRecalc();
+        RenderBlock* nextBlock = toRenderBlock(next);
+        RenderBlock* prevBlock = toRenderBlock(prev);
+       
+        if (prev->childrenInline() != next->childrenInline()) {
+            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::createAnonymousStyle(style());
+            children()->removeChildNode(this, inlineChildrenBlock, inlineChildrenBlock->hasLayer());
+            inlineChildrenBlock->setStyle(newStyle);
+            
+            // Now just put the inlineChildrenBlock inside the blockChildrenBlock.
+            blockChildrenBlock->children()->insertChildNode(blockChildrenBlock, inlineChildrenBlock, prev == inlineChildrenBlock ? blockChildrenBlock->firstChild() : 0,
+                                                            inlineChildrenBlock->hasLayer() || blockChildrenBlock->hasLayer());
+            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;
+            else
+                next = 0;
+        } else {
+            // Take all the children out of the |next| block and put them in
+            // the |prev| block.
+            nextBlock->moveAllChildrenTo(prevBlock, nextBlock->hasLayer() || prevBlock->hasLayer());        
+            
+            // Delete the now-empty block's lines and nuke it.
+            nextBlock->deleteLineBoxTree();
+            nextBlock->destroy();
+            next = 0;
+        }
+    }
+
+    RenderBox::removeChild(oldChild);
+
+    RenderObject* child = prev ? prev : next;
+    if (canMergeAnonymousBlocks && child && !child->previousSibling() && !child->nextSibling() && !isFlexibleBoxIncludingDeprecated()) {
+        // 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.
+        setNeedsLayoutAndPrefWidthsRecalc();
+        setChildrenInline(child->childrenInline());
+        RenderBlock* anonBlock = toRenderBlock(children()->removeChildNode(this, child, child->hasLayer()));
+        anonBlock->moveAllChildrenTo(this, child->hasLayer());
+        // Delete the now-empty block's lines and nuke it.
+        anonBlock->deleteLineBoxTree();
+        anonBlock->destroy();
+    }
+
+    if (!firstChild() && !documentBeingDestroyed()) {
+        // If this was our last child be sure to clear out our line boxes.
+        if (childrenInline())
+            lineBoxes()->deleteLineBoxes(renderArena());
+    }
+}
+
+bool RenderBlock::isSelfCollapsingBlock() const
+{
+    // We are not self-collapsing if we
+    // (a) have a non-zero height according to layout (an optimization to avoid wasting time)
+    // (b) are a table,
+    // (c) have border/padding,
+    // (d) have a min-height
+    // (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)
+        return false;
+
+    Length logicalHeightLength = style()->logicalHeight();
+    bool hasAutoHeight = logicalHeightLength.isAuto();
+    if (logicalHeightLength.isPercent() && !document()->inQuirksMode()) {
+        hasAutoHeight = true;
+        for (RenderBlock* cb = containingBlock(); !cb->isRenderView(); 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->isFloatingOrPositioned())
+                continue;
+            if (!child->isSelfCollapsingBlock())
+                return false;
+        }
+        return true;
+    }
+    return false;
+}
+
+void RenderBlock::startDelayUpdateScrollInfo()
+{
+    if (gDelayUpdateScrollInfo == 0) {
+        ASSERT(!gDelayedUpdateScrollInfoSet);
+        gDelayedUpdateScrollInfoSet = new DelayedUpdateScrollInfoSet;
+    }
+    ASSERT(gDelayedUpdateScrollInfoSet);
+    ++gDelayUpdateScrollInfo;
+}
+
+void RenderBlock::finishDelayUpdateScrollInfo()
+{
+    --gDelayUpdateScrollInfo;
+    ASSERT(gDelayUpdateScrollInfo >= 0);
+    if (gDelayUpdateScrollInfo == 0) {
+        ASSERT(gDelayedUpdateScrollInfoSet);
+
+        OwnPtr<DelayedUpdateScrollInfoSet> infoSet(adoptPtr(gDelayedUpdateScrollInfoSet));
+        gDelayedUpdateScrollInfoSet = 0;
+
+        for (DelayedUpdateScrollInfoSet::iterator it = infoSet->begin(); it != infoSet->end(); ++it) {
+            RenderBlock* block = *it;
+            if (block->hasOverflowClip()) {
+                block->layer()->updateScrollInfoAfterLayout();
+            }
+        }
+    }
+}
+
+void RenderBlock::updateScrollInfoAfterLayout()
+{
+    if (hasOverflowClip()) {
+        if (gDelayUpdateScrollInfo)
+            gDelayedUpdateScrollInfoSet->add(this);
+        else
+            layer()->updateScrollInfoAfterLayout();
+    }
+}
+
+void RenderBlock::layout()
+{
+    // Update our first letter info now.
+    updateFirstLetter();
+
+    // Table cells call layoutBlock directly, so don't add any logic here.  Put code into
+    // layoutBlock().
+    layoutBlock(false);
+    
+    // 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)
+        clearLayoutOverflow();
+}
+
+void RenderBlock::layoutBlock(bool relayoutChildren, LayoutUnit pageLogicalHeight, BlockLayoutPass layoutPass)
+{
+    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, everHadLayout() && checkForRepaintDuringLayout());
+
+    LayoutUnit oldWidth = logicalWidth();
+    LayoutUnit oldColumnWidth = desiredColumnWidth();
+
+    computeLogicalWidth();
+    calcColumnWidth();
+
+    m_overflow.clear();
+
+    if (oldWidth != logicalWidth() || oldColumnWidth != desiredColumnWidth())
+        relayoutChildren = true;
+
+    // If nothing changed about our floating positioned objects, let's go ahead and try to place them as
+    // floats to avoid doing two passes.
+    BlockLayoutPass floatsLayoutPass = layoutPass;
+    if (floatsLayoutPass == NormalLayoutPass && !relayoutChildren && !positionedFloatsNeedRelayout())
+        floatsLayoutPass = PositionedFloatLayoutPass;
+    clearFloats(floatsLayoutPass);
+
+    LayoutUnit previousHeight = logicalHeight();
+    setLogicalHeight(0);
+    bool hasSpecifiedPageLogicalHeight = false;
+    bool pageLogicalHeightChanged = false;
+    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.
+            computeLogicalHeight();
+            LayoutUnit columnHeight = contentLogicalHeight();
+            if (columnHeight > 0) {
+                pageLogicalHeight = columnHeight;
+                hasSpecifiedPageLogicalHeight = true;
+            }
+            setLogicalHeight(0);
+        }
+        if (colInfo->columnHeight() != pageLogicalHeight && everHadLayout()) {
+            colInfo->setColumnHeight(pageLogicalHeight);
+            pageLogicalHeightChanged = true;
+        }
+        
+        if (!hasSpecifiedPageLogicalHeight && !pageLogicalHeight)
+            colInfo->clearForcedBreaks();
+    }
+
+    RenderView* renderView = view();
+    LayoutStateMaintainer statePusher(renderView, this, locationOffset(), hasColumns() || hasTransform() || hasReflection() || style()->isFlippedBlocksWritingMode(), pageLogicalHeight, pageLogicalHeightChanged, colInfo);
+    
+    if (inRenderFlowThread()) {
+        // Regions changing widths can force us to relayout our children.
+        if (logicalWidthChangedInRegions())
+            relayoutChildren = true;
+    
+        // 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.
+        LayoutUnit oldHeight =  logicalHeight();
+        LayoutUnit oldLogicalTop = logicalTop();
+        setLogicalHeight(numeric_limits<LayoutUnit>::max() / 2); 
+        computeLogicalHeight();
+        enclosingRenderFlowThread()->setRegionRangeForBox(this, offsetFromLogicalTopOfFirstPage());
+        setLogicalHeight(oldHeight);
+        setLogicalTop(oldLogicalTop);
+    }
+
+    // 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();
+        
+        setMarginBeforeQuirk(style()->marginBefore().quirk());
+        setMarginAfterQuirk(style()->marginAfter().quirk());
+
+        Node* n = node();
+        if (n && n->hasTagName(formTag) && static_cast<HTMLFormElement*>(n)->isMalformed()) {
+            // See if this form is malformed (i.e., unclosed). If so, don't give the form
+            // a bottom margin.
+            setMaxMarginAfterValues(0, 0);
+        }
+        
+        setPaginationStrut(0);
+    }
+
+    // For overflow:scroll blocks, ensure we have both scrollbars in place always.
+    if (scrollsOverflow()) {
+        if (style()->overflowX() == OSCROLL)
+            layer()->setHasHorizontalScrollbar(true);
+        if (style()->overflowY() == OSCROLL)
+            layer()->setHasVerticalScrollbar(true);
+    }
+
+    LayoutUnit repaintLogicalTop = 0;
+    LayoutUnit repaintLogicalBottom = 0;
+    LayoutUnit maxFloatLogicalBottom = 0;
+    if (!firstChild() && !isAnonymousBlock())
+        setChildrenInline(true);
+    if (childrenInline())
+        layoutInlineChildren(relayoutChildren, repaintLogicalTop, repaintLogicalBottom);
+    else
+        layoutBlockChildren(relayoutChildren, maxFloatLogicalBottom);
+
+    // Expand our intrinsic height to encompass floats.
+    LayoutUnit toAdd = borderAfter() + paddingAfter() + scrollbarLogicalHeight();
+    if (lowestFloatLogicalBottom() > (logicalHeight() - toAdd) && expandsToEncloseOverhangingFloats())
+        setLogicalHeight(lowestFloatLogicalBottom() + toAdd);
+    
+    if (layoutColumns(hasSpecifiedPageLogicalHeight, pageLogicalHeight, statePusher))
+        return;
+ 
+    // Calculate our new height.
+    LayoutUnit oldHeight = logicalHeight();
+    LayoutUnit oldClientAfterEdge = clientLogicalBottom();
+    computeLogicalHeight();
+    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->isFloatingOrPositioned()) {
+                    RenderBlock* block = toRenderBlock(child);
+                    if (block->lowestFloatLogicalBottomIncludingPositionedFloats() + block->logicalTop() > newHeight)
+                        addOverhangingFloats(block, false);
+                }
+            }
+        }
+    }
+
+    if (previousHeight != newHeight)
+        relayoutChildren = true;
+
+    bool needAnotherLayoutPass = layoutPositionedObjects(relayoutChildren || isRoot());
+
+    if (inRenderFlowThread())
+        enclosingRenderFlowThread()->setRegionRangeForBox(this, offsetFromLogicalTopOfFirstPage());
+
+    // Add overflow from children (unless we're multi-column, since in that case all our child overflow is clipped anyway).
+    computeOverflow(oldClientAfterEdge);
+    
+    statePusher.pop();
+
+    if (renderView->layoutState()->m_pageLogicalHeight)
+        setPageLogicalOffset(renderView->layoutState()->pageLogicalOffset(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 && (style()->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(-layer()->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()) {
+            // FIXME: Might need rounding once we switch to float, see https://bugs.webkit.org/show_bug.cgi?id=64021
+            repaintRectangle(repaintRect); // We need to do a partial repaint of our content.
+            if (hasReflection())
+                repaintRectangle(reflectedRect(repaintRect));
+        }
+    }
+    
+    if (needAnotherLayoutPass && layoutPass == NormalLayoutPass) {
+        setChildNeedsLayout(true, false);
+        layoutBlock(false, pageLogicalHeight, PositionedFloatLayoutPass);
+    } else
+        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);
+        }
+    }
+}
+
+void RenderBlock::computeOverflow(LayoutUnit oldClientAfterEdge, bool recomputeFloats)
+{
+    // Add overflow from children.
+    addOverflowFromChildren();
+
+    if (!hasColumns() && (recomputeFloats || isRoot() || expandsToEncloseOverhangingFloats() || hasSelfPaintingLayer()))
+        addOverflowFromFloats();
+
+    // Add in the overflow from positioned objects.
+    addOverflowFromPositionedObjects();
+
+    if (hasOverflowClip()) {
+        // 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 rectToApply;
+        if (isHorizontalWritingMode())
+            rectToApply = LayoutRect(clientRect.x(), clientRect.y(), 1, max<LayoutUnit>(0, oldClientAfterEdge - clientRect.y()));
+        else
+            rectToApply = LayoutRect(clientRect.x(), clientRect.y(), max<LayoutUnit>(0, oldClientAfterEdge - clientRect.x()), 1);
+        addLayoutOverflow(rectToApply);
+    }
+        
+    // Add visual overflow from box-shadow and border-image-outset.
+    addVisualEffectOverflow();
+
+    // Add visual overflow from theme.
+    addVisualOverflowFromTheme();
+}
+
+void RenderBlock::addOverflowFromBlockChildren()
+{
+    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
+        if (!child->isFloatingOrPositioned())
+            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->m_isDescendant && !r->m_renderer->isPositioned())
+            addOverflowFromChild(r->m_renderer, IntSize(xPositionForFloatIncludingMargin(r), yPositionForFloatIncludingMargin(r)));
+    }
+    return;
+}
+
+void RenderBlock::addOverflowFromPositionedObjects()
+{
+    if (!m_positionedObjects)
+        return;
+
+    RenderBox* positionedObject;
+    Iterator end = m_positionedObjects->end();
+    for (Iterator it = m_positionedObjects->begin(); it != end; ++it) {
+        positionedObject = *it;
+        
+        // Fixed positioned elements don't contribute to layout overflow, since they don't scroll with the content.
+        if (positionedObject->style()->position() != FixedPosition)
+            addOverflowFromChild(positionedObject);
+    }
+}
+
+void RenderBlock::addVisualOverflowFromTheme()
+{
+    if (!style()->hasAppearance())
+        return;
+
+    IntRect inflatedRect = borderBoxRect();
+    theme()->adjustRepaintRect(this, inflatedRect);
+    addVisualOverflow(inflatedRect);
+}
+
+bool RenderBlock::expandsToEncloseOverhangingFloats() const
+{
+    return isInlineBlockOrInlineTable() || isFloatingOrPositioned() || hasOverflowClip() || (parent() && parent()->isDeprecatedFlexibleBox())
+           || hasColumns() || isTableCell() || isFieldset() || isWritingModeRoot() || isRoot();
+}
+
+void RenderBlock::adjustPositionedBlock(RenderBox* child, const MarginInfo& marginInfo)
+{
+    bool isHorizontal = isHorizontalWritingMode();
+    bool hasStaticBlockPosition = child->style()->hasStaticBlockPosition(isHorizontal);
+    
+    LayoutUnit logicalTop = logicalHeight();
+    setStaticInlinePositionForChild(child, logicalTop, startOffsetForContent(logicalTop));
+
+    if (!marginInfo.canCollapseWithMarginBefore()) {
+        child->computeBlockDirectionMargins(this);
+        LayoutUnit marginBefore = marginBeforeForChild(child);
+        LayoutUnit collapsedBeforePos = marginInfo.positiveMargin();
+        LayoutUnit collapsedBeforeNeg = marginInfo.negativeMargin();
+        if (marginBefore > 0) {
+            if (marginBefore > collapsedBeforePos)
+                collapsedBeforePos = marginBefore;
+        } else {
+            if (-marginBefore > collapsedBeforeNeg)
+                collapsedBeforeNeg = -marginBefore;
+        }
+        logicalTop += (collapsedBeforePos - collapsedBeforeNeg) - marginBefore;
+    }
+    
+    RenderLayer* childLayer = child->layer();
+    if (childLayer->staticBlockPosition() != logicalTop) {
+        childLayer->setStaticBlockPosition(logicalTop);
+        if (hasStaticBlockPosition)
+            child->setChildNeedsLayout(true, false);
+    }
+}
+
+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() ? 0 : marginInfo.margin();
+    setLogicalHeight(logicalHeight() + marginOffset);
+    positionNewFloats();
+    setLogicalHeight(logicalHeight() - marginOffset);
+}
+
+bool RenderBlock::handleSpecialChild(RenderBox* child, const MarginInfo& marginInfo)
+{
+    // Handle in the given order
+    return handlePositionedChild(child, marginInfo)
+        || handleFloatingChild(child, marginInfo)
+        || handleRunInChild(child);
+}
+
+
+bool RenderBlock::handlePositionedChild(RenderBox* child, const MarginInfo& marginInfo)
+{
+    if (child->isPositioned()) {
+        child->containingBlock()->insertPositionedObject(child);
+        adjustPositionedBlock(child, marginInfo);
+        return true;
+    }
+    return false;
+}
+
+bool RenderBlock::handleFloatingChild(RenderBox* child, const MarginInfo& marginInfo)
+{
+    if (child->isFloating()) {
+        insertFloatingObject(child);
+        adjustFloatingBlock(marginInfo);
+        return true;
+    }
+    return false;
+}
+
+bool RenderBlock::handleRunInChild(RenderBox* child)
+{
+    // See if we have a run-in element with inline children.  If the
+    // children aren't inline, then just treat the run-in as a normal
+    // block.
+    if (!child->isRunIn() || !child->childrenInline())
+        return false;
+    // FIXME: We don't handle non-block elements with run-in for now.
+    if (!child->isRenderBlock())
+        return false;
+
+    RenderBlock* blockRunIn = toRenderBlock(child);
+    RenderObject* curr = blockRunIn->nextSibling();
+    if (!curr || !curr->isRenderBlock() || !curr->childrenInline() || curr->isRunIn() || curr->isAnonymous() || curr->isFloatingOrPositioned())
+        return false;
+
+    RenderBlock* currBlock = toRenderBlock(curr);
+
+    // First we destroy any :before/:after content. It will be regenerated by the new inline.
+    // Exception is if the run-in itself is generated.
+    if (child->style()->styleType() != BEFORE && child->style()->styleType() != AFTER) {
+        RenderObject* generatedContent;
+        if (child->getCachedPseudoStyle(BEFORE) && (generatedContent = child->beforePseudoElementRenderer()))
+            generatedContent->destroy();
+        if (child->getCachedPseudoStyle(AFTER) && (generatedContent = child->afterPseudoElementRenderer()))
+            generatedContent->destroy();
+    }
+
+    // Remove the old child.
+    children()->removeChildNode(this, blockRunIn);
+
+    // Create an inline.
+    Node* runInNode = blockRunIn->node();
+    RenderInline* inlineRunIn = new (renderArena()) RenderInline(runInNode ? runInNode : document());
+    inlineRunIn->setStyle(blockRunIn->style());
+
+    // Move the nodes from the old child to the new child
+    for (RenderObject* runInChild = blockRunIn->firstChild(); runInChild;) {
+        RenderObject* nextSibling = runInChild->nextSibling();
+        blockRunIn->children()->removeChildNode(blockRunIn, runInChild, false);
+        inlineRunIn->addChild(runInChild); // Use addChild instead of appendChildNode since it handles correct placement of the children relative to :after-generated content.
+        runInChild = nextSibling;
+    }
+
+    // Now insert the new child under |currBlock|. Use addChild instead of insertChildNode since it handles correct placement of the children, esp where we cannot insert
+    // anything before the first child. e.g. details tag. See https://bugs.webkit.org/show_bug.cgi?id=58228.
+    currBlock->addChild(inlineRunIn, currBlock->firstChild());
+    
+    // If the run-in had an element, we need to set the new renderer.
+    if (runInNode)
+        runInNode->setRenderer(inlineRunIn);
+
+    // Destroy the block run-in, which includes deleting its line box tree.
+    blockRunIn->deleteLineBoxTree();
+    blockRunIn->destroy();
+
+    // The block acts like an inline, so just null out its
+    // position.
+    
+    return true;
+}
+
+LayoutUnit RenderBlock::collapseMargins(RenderBox* child, MarginInfo& marginInfo)
+{
+    // 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 (child->isSelfCollapsingBlock()) {
+        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 = child->isMarginBeforeQuirk() || style()->marginBeforeCollapse() == MDISCARD;
+
+    if (marginInfo.canCollapseWithMarginBefore()) {
+        // 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)) {
+            setMarginBeforeQuirk(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.
+            setMarginBeforeQuirk(true);
+    }
+
+    if (marginInfo.quirkContainer() && marginInfo.atBeforeSideOfBlock() && (posTop - negTop))
+        marginInfo.setMarginBeforeQuirk(topQuirk);
+
+    LayoutUnit beforeCollapseLogicalTop = logicalHeight();
+    LayoutUnit logicalTop = beforeCollapseLogicalTop;
+    if (child->isSelfCollapsingBlock()) {
+        // 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 (child->style()->marginBeforeCollapse() == MSEPARATE) {
+            setLogicalHeight(logicalHeight() + marginInfo.margin() + marginBeforeForChild(child));
+            logicalTop = logicalHeight();
+        }
+        else if (!marginInfo.atBeforeSideOfBlock() ||
+            (!marginInfo.canCollapseMarginBeforeWithChildren()
+             && (!document()->inQuirksMode() || !marginInfo.quirkContainer() || !marginInfo.marginBeforeQuirk()))) {
+            // 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.setPositiveMargin(childMargins.positiveMarginAfter());
+        marginInfo.setNegativeMargin(childMargins.negativeMarginAfter());
+
+        if (marginInfo.margin())
+            marginInfo.setMarginAfterQuirk(child->isMarginAfterQuirk() || style()->marginAfterCollapse() == MDISCARD);
+    }
+    
+    // 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));
+    }
+    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()) {
+        // 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.
+        // CSS2.1 states:
+        // "An element that has had clearance applied to it never collapses its top margin with its parent block's bottom margin.
+        // Therefore if we are at the bottom of the block, let's go ahead and reset margins to only include the
+        // self-collapsing block's bottom margin.
+        bool atBottomOfBlock = true;
+        for (RenderBox* curr = child->nextSiblingBox(); curr && atBottomOfBlock; curr = curr->nextSiblingBox()) {
+            if (!curr->isFloatingOrPositioned())
+                atBottomOfBlock = false;
+        }
+        
+        MarginValues childMargins = marginValuesForChild(child);
+        if (atBottomOfBlock) {
+            marginInfo.setPositiveMargin(childMargins.positiveMarginAfter());
+            marginInfo.setNegativeMargin(childMargins.negativeMarginAfter());
+        } else {
+            marginInfo.setPositiveMargin(max(childMargins.positiveMarginBefore(), childMargins.positiveMarginAfter()));
+            marginInfo.setNegativeMargin(max(childMargins.negativeMarginBefore(), childMargins.negativeMarginAfter()));
+        }
+        
+        // Adjust our height such that we are ready to be collapsed with subsequent siblings (or the bottom
+        // of the parent block).
+        setLogicalHeight(child->y() - max<LayoutUnit>(0, marginInfo.margin()));
+    } else
+        // Increase our height by the amount we had to clear.
+        setLogicalHeight(height() + 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);
+    }
+    
+    return yPos + heightIncrease;
+}
+
+LayoutUnit RenderBlock::estimateLogicalTopPosition(RenderBox* child, const MarginInfo& marginInfo, LayoutUnit& estimateWithoutPagination)
+{
+    // 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 childMarginBefore = child->selfNeedsLayout() ? marginBeforeForChild(child) : collapsedMarginBeforeForChild(child);
+        logicalTopEstimate += max(marginInfo.margin(), childMarginBefore);
+    }
+
+    // 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();
+    }
+
+    return logicalTopEstimate;
+}
+
+LayoutUnit RenderBlock::computeStartPositionDeltaForChildAvoidingFloats(const RenderBox* child, LayoutUnit childMarginStart,
+    LayoutUnit childLogicalWidth, RenderRegion* region, LayoutUnit offsetFromLogicalTopOfFirstPage)
+{
+    LayoutUnit startPosition = startOffsetForContent(region, offsetFromLogicalTopOfFirstPage);
+
+    // Add in our start margin.
+    LayoutUnit oldPosition = startPosition + childMarginStart;
+    LayoutUnit newPosition = oldPosition;
+
+    LayoutUnit blockOffset = logicalTopForChild(child);
+    if (region)
+        blockOffset = max(blockOffset, blockOffset + (region->offsetFromLogicalTopOfFirstPage() - offsetFromLogicalTopOfFirstPage));
+
+    LayoutUnit startOff = startOffsetForLine(blockOffset, false, region, offsetFromLogicalTopOfFirstPage);
+    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.
+        // FIXME: Needs to use epsilon once we switch to float, see https://bugs.webkit.org/show_bug.cgi?id=64021
+    } else if (startOff != startPosition) {
+        // The object is shifting to the "end" side of the block. The object might be centered, so we need to
+        // recalculate our inline direction margins. Note that the containing block content
+        // width computation will take into account the delta between |startOff| and |startPosition|
+        // so that we can just pass the content width in directly to the |computeMarginsInContainingBlockInlineDirection|
+        // function.
+        LayoutUnit oldMarginStart = marginStartForChild(child);
+        LayoutUnit oldMarginEnd = marginEndForChild(child);
+        RenderBox* mutableChild = const_cast<RenderBox*>(child);
+        mutableChild->computeInlineDirectionMargins(this,
+            availableLogicalWidthForLine(blockOffset, false, region, offsetFromLogicalTopOfFirstPage), childLogicalWidth);
+        newPosition = startOff + marginStartForChild(child);
+        if (inRenderFlowThread()) {
+            setMarginStartForChild(mutableChild, oldMarginStart);
+            setMarginEndForChild(mutableChild, oldMarginEnd);
+        }
+    }
+    
+    return newPosition - oldPosition;
+}
+
+void RenderBlock::determineLogicalLeftPositionForChild(RenderBox* child)
+{
+    LayoutUnit startPosition = borderStart() + paddingStart();
+    LayoutUnit totalAvailableLogicalWidth = borderAndPaddingLogicalWidth() + availableLogicalWidth();
+
+    // 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() && !inRenderFlowThread())
+        newPosition += computeStartPositionDeltaForChildAvoidingFloats(child, marginStartForChild(child), logicalWidthForChild(child));
+
+    setLogicalLeftForChild(child, style()->isLeftToRightDirection() ? newPosition : totalAvailableLogicalWidth - newPosition - logicalWidthForChild(child), ApplyLayoutDelta);
+}
+
+void RenderBlock::setCollapsedBottomMargin(const MarginInfo& marginInfo)
+{
+    if (marginInfo.canCollapseWithMarginAfter() && !marginInfo.canCollapseWithMarginBefore()) {
+        // 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.marginAfterQuirk())
+            setMarginAfterQuirk(false);
+
+        if (marginInfo.marginAfterQuirk() && marginAfter() == 0)
+            // 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.
+            setMarginAfterQuirk(true);
+    }
+}
+
+void RenderBlock::handleAfterSideOfBlock(LayoutUnit beforeSide, LayoutUnit afterSide, MarginInfo& marginInfo)
+{
+    marginInfo.setAtAfterSideOfBlock(true);
+
+    // If we can't collapse with children then go ahead and add in the bottom margin.
+    if (!marginInfo.canCollapseWithMarginAfter() && !marginInfo.canCollapseWithMarginBefore()
+        && (!document()->inQuirksMode() || !marginInfo.quirkContainer() || !marginInfo.marginAfterQuirk()))
+        setLogicalHeight(logicalHeight() + marginInfo.margin());
+        
+    // Now add in our bottom border/padding.
+    setLogicalHeight(logicalHeight() + afterSide);
+
+    // 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));
+
+    // Update our bottom collapsed margin info.
+    setCollapsedBottomMargin(marginInfo);
+}
+
+void RenderBlock::setLogicalLeftForChild(RenderBox* child, LayoutUnit logicalLeft, ApplyLayoutDeltaMode applyDelta)
+{
+    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);
+    }
+}
+
+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);
+    }
+}
+
+void RenderBlock::layoutBlockChildren(bool relayoutChildren, LayoutUnit& maxFloatLogicalBottom)
+{
+    if (gPercentHeightDescendantsMap) {
+        if (HashSet<RenderBox*>* descendants = gPercentHeightDescendantsMap->get(this)) {
+            HashSet<RenderBox*>::iterator end = descendants->end();
+            for (HashSet<RenderBox*>::iterator it = descendants->begin(); it != end; ++it) {
+                RenderBox* box = *it;
+                while (box != this) {
+                    if (box->normalChildNeedsLayout())
+                        break;
+                    box->setChildNeedsLayout(true, false);
+                    box = box->containingBlock();
+                    ASSERT(box);
+                    if (!box)
+                        break;
+                }
+            }
+        }
+    }
+
+    LayoutUnit beforeEdge = borderBefore() + paddingBefore();
+    LayoutUnit afterEdge = borderAfter() + paddingAfter() + scrollbarLogicalHeight();
+
+    setLogicalHeight(beforeEdge);
+
+    // The margin struct caches all our current margin collapsing state.  The compact struct caches state when we encounter compacts,
+    MarginInfo marginInfo(this, beforeEdge, afterEdge);
+
+    // 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);
+
+    LayoutUnit previousFloatLogicalBottom = 0;
+    maxFloatLogicalBottom = 0;
+
+    RenderBox* next = firstChildBox();
+
+    while (next) {
+        RenderBox* child = next;
+        next = child->nextSiblingBox();
+
+        if (childToExclude == child)
+            continue; // Skip this child, since it will be positioned by the specialized subclass (fieldsets and ruby runs).
+
+        // Make sure we layout children if they need it.
+        // 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->style()->logicalHeight().isPercent() || child->style()->logicalMinHeight().isPercent() || child->style()->logicalMaxHeight().isPercent()) && !isRenderView()))
+            child->setChildNeedsLayout(true, false);
+
+        // 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, false);
+
+        // Handle the four types of special elements first.  These include positioned content, floating content, compacts and
+        // run-ins.  When we encounter these four types of objects, we don't actually lay them out as normal flow blocks.
+        if (handleSpecialChild(child, marginInfo))
+            continue;
+
+        // Lay out the child.
+        layoutBlockChild(child, marginInfo, previousFloatLogicalBottom, maxFloatLogicalBottom);
+    }
+    
+    // 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->computeBlockDirectionMargins(this);
+
+    // Do not allow a collapse if the margin-before-collapse style is set to SEPARATE.
+    if (child->style()->marginBeforeCollapse() == MSEPARATE) {
+        marginInfo.setAtBeforeSideOfBlock(false);
+        marginInfo.clearMargin();
+    }
+
+    // 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->x(), child->y() , child->width(), child->height());
+    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;
+    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, lowestFloatLogicalBottomIncludingPositionedFloats());
+        if (fb > logicalTopEstimate)
+            markDescendantsWithFloats = true;
+    }
+
+    if (childRenderBlock) {
+        if (markDescendantsWithFloats)
+            childRenderBlock->markAllDescendantsWithFloatsForLayout();
+        if (!child->isWritingModeRoot())
+            previousFloatLogicalBottom = max(previousFloatLogicalBottom, oldLogicalTop + childRenderBlock->lowestFloatLogicalBottomIncludingPositionedFloats());
+    }
+
+    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.
+    if (logicalTopAfterClear != logicalTopEstimate) {
+        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, false);
+        }
+        
+        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);
+
+    // Update our height now that the child has been placed in the correct position.
+    setLogicalHeight(logicalHeight() + logicalHeightForChild(child));
+    if (child->style()->marginAfterCollapse() == MSEPARATE) {
+        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->x() - oldRect.x(), child->y() - oldRect.y());
+    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(oldLayoutDelta == view()->layoutDelta());
+}
+
+void RenderBlock::simplifiedNormalFlowLayout()
+{
+    if (childrenInline()) {
+        ListHashSet<RootInlineBox*> lineBoxes;
+        for (InlineWalker walker(this); !walker.atEnd(); walker.advance()) {
+            RenderObject* o = walker.current();
+            if (!o->isPositioned() && (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->isPositioned())
+                box->layoutIfNeeded();
+        }
+    }
+}
+
+bool RenderBlock::simplifiedLayout()
+{
+    if ((!posChildNeedsLayout() && !needsSimplifiedNormalFlowLayout()) || normalChildNeedsLayout() || selfNeedsLayout())
+        return false;
+
+    LayoutStateMaintainer statePusher(view(), this, IntSize(x(), y()), 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.
+    if (posChildNeedsLayout() && layoutPositionedObjects(false))
+        return false; // If a positioned float is causing our normal flow to change, then we have to bail and do a full layout.
+
+    // 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.
+    m_overflow.clear();
+    computeOverflow(clientLogicalBottom(), true);
+
+    statePusher.pop();
+    
+    updateLayerTransform();
+
+    updateScrollInfoAfterLayout();
+
+    setNeedsLayout(false);
+    return true;
+}
+
+bool RenderBlock::positionedFloatsNeedRelayout()
+{
+    if (!hasPositionedFloats())
+        return false;
+    
+    RenderBox* positionedObject;
+    Iterator end = m_positionedObjects->end();
+    for (Iterator it = m_positionedObjects->begin(); it != end; ++it) {
+        positionedObject = *it;
+        if (!positionedObject->isFloating())
+            continue;
+
+        if (positionedObject->needsLayout())
+            return true;
+
+        if (positionedObject->style()->hasStaticBlockPosition(isHorizontalWritingMode()) && positionedObject->parent() != this && positionedObject->parent()->isBlockFlow())
+            return true;
+        
+        if (view()->layoutState()->pageLogicalHeightChanged() || (view()->layoutState()->pageLogicalHeight() && view()->layoutState()->pageLogicalOffset(logicalTop()) != pageLogicalOffset()))
+            return true;
+    }
+    
+    return false;
+}
+
+bool RenderBlock::layoutPositionedObjects(bool relayoutChildren)
+{
+    if (!m_positionedObjects)
+        return false;
+        
+    if (hasColumns())
+        view()->layoutState()->clearPaginationInformation(); // Positioned objects are not part of the column flow, so they don't paginate with the columns.
+
+    bool didFloatingBoxRelayout = false;
+
+    RenderBox* r;
+    Iterator end = m_positionedObjects->end();
+    for (Iterator it = m_positionedObjects->begin(); it != end; ++it) {
+        r = *it;
+        // 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, false);
+            
+        // 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, false);
+        
+        if (!r->needsLayout())
+            r->markForPaginationRelayoutIfNeeded();
+        
+        // FIXME: Technically we could check the old placement and the new placement of the box and only invalidate if
+        // the margin box of the object actually changed.
+        if (r->needsLayout() && r->isFloating())
+            didFloatingBoxRelayout = true;
+
+        // 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 in a flow thread, go ahead and compute a vertical position for our object now.
+        // If it's wrong we'll lay out again.
+        LayoutUnit oldLogicalTop = 0;
+        bool checkForPaginationRelayout = r->needsLayout() && view()->layoutState()->isPaginated() && view()->layoutState()->pageLogicalHeight(); 
+        if (checkForPaginationRelayout) {
+            if (isHorizontalWritingMode() == r->isHorizontalWritingMode())
+                r->computeLogicalHeight();
+            else
+                r->computeLogicalWidth();
+            oldLogicalTop = logicalTopForChild(r);
+        }
+            
+        r->layoutIfNeeded();
+        
+        // Lay out again if our estimate was wrong.
+        if (checkForPaginationRelayout && logicalTopForChild(r) != oldLogicalTop) {
+            r->setChildNeedsLayout(true, false);
+            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.
+        
+    return didFloatingBoxRelayout;
+}
+
+void RenderBlock::markPositionedObjectsForLayout()
+{
+    if (m_positionedObjects) {
+        RenderBox* r;
+        Iterator end = m_positionedObjects->end();
+        for (Iterator it = m_positionedObjects->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(logicalTop()) != pageLogicalOffset()))
+        setChildNeedsLayout(true, false);
+}
+
+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->m_shouldPaint) && !r->m_renderer->hasSelfPaintingLayer()) {
+            r->m_renderer->repaint();
+            r->m_renderer->repaintOverhangingFloats();
+        }
+    }
+}
+ 
+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 = visualOverflowRect();
+        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))
+        layer()->paintOverflowControls(paintInfo.context, 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 && ruleThickness <= colGap;
+    if (!renderRule)
+        return;
+
+    ColumnInfo* colInfo = columnInfo();
+    unsigned colCount = columnCount(colInfo);
+
+    bool antialias = shouldAntialiasLines(paintInfo.context);
+
+    if (colInfo->progressionAxis() == ColumnInfo::InlineAxis) {
+        LayoutUnit currLogicalLeftOffset = style()->isLeftToRightDirection() ? 0 : contentLogicalWidth();
+        LayoutUnit ruleAdd = logicalLeftOffsetForContent();
+        LayoutUnit ruleLogicalLeft = style()->isLeftToRightDirection() ? 0 : contentLogicalWidth();
+        LayoutUnit inlineDirectionSize = colInfo->desiredColumnWidth();
+        BoxSide boxSide = isHorizontalWritingMode()
+            ? style()->isLeftToRightDirection() ? BSLeft : BSRight
+            : style()->isLeftToRightDirection() ? BSTop : BSBottom;
+
+        for (unsigned i = 0; i < colCount; i++) {
+            // Move to the next position.
+            if (style()->isLeftToRightDirection()) {
+                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;
+                drawLineForBoxSide(paintInfo.context, ruleLeft, ruleTop, ruleRight, ruleBottom, boxSide, ruleColor, ruleStyle, 0, 0, antialias);
+            }
+            
+            ruleLogicalLeft = currLogicalLeftOffset;
+        }
+    } else {
+        LayoutUnit ruleLeft = isHorizontalWritingMode() ? borderLeft() + paddingLeft() : colGap / 2 - colGap - ruleThickness / 2 + borderBefore() + paddingBefore();
+        LayoutUnit ruleWidth = isHorizontalWritingMode() ? contentWidth() : ruleThickness;
+        LayoutUnit ruleTop = isHorizontalWritingMode() ? colGap / 2 - colGap - ruleThickness / 2 + borderBefore() + paddingBefore() : borderStart() + paddingStart();
+        LayoutUnit ruleHeight = isHorizontalWritingMode() ? ruleThickness : contentHeight();
+        LayoutRect ruleRect(ruleLeft, ruleTop, ruleWidth, ruleHeight);
+
+        flipForWritingMode(ruleRect);
+        ruleRect.moveBy(paintOffset);
+
+        BoxSide boxSide = isHorizontalWritingMode()
+            ? !style()->isFlippedBlocksWritingMode() ? BSTop : BSBottom
+            : !style()->isFlippedBlocksWritingMode() ? BSLeft : BSRight;
+
+        LayoutSize step(0, !style()->isFlippedBlocksWritingMode() ? colInfo->columnHeight() + colGap : -(colInfo->columnHeight() + colGap));
+        if (!isHorizontalWritingMode())
+            step = step.transposedSize();
+
+        for (unsigned i = 1; i < colCount; i++) {
+            ruleRect.move(step);
+            drawLineForBoxSide(paintInfo.context, ruleRect.x(), ruleRect.y(), ruleRect.maxX(), ruleRect.maxY(), boxSide, ruleColor, ruleStyle, 0, 0, antialias);
+        }
+    }
+}
+
+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 currLogicalTopOffset = 0;
+    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);
+        if (colInfo->progressionAxis() == ColumnInfo::BlockAxis) {
+            if (isHorizontalWritingMode())
+                offset.expand(0, colRect.y() - borderTop() - paddingTop());
+            else
+                offset.expand(colRect.x() - borderLeft() - paddingLeft(), 0);
+        }
+        colRect.moveBy(paintOffset);
+        PaintInfo info(paintInfo);
+        info.rect.intersect(colRect);
+        
+        if (!info.rect.isEmpty()) {
+            GraphicsContextStateSaver stateSaver(*context);
+            
+            // Each strip pushes a clip, since column boxes are specified as being
+            // like overflow:hidden.
+            context->clip(colRect);
+
+            // 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);
+        }
+
+        LayoutUnit blockDelta = (isHorizontalWritingMode() ? colRect.height() : colRect.width());
+        if (style()->isFlippedBlocksWritingMode())
+            currLogicalTopOffset += blockDelta;
+        else
+            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, updateStyleSelector on the Document
+    // will do a full repaint().
+    if (document()->didLayoutWithPendingStylesheets() && !isRenderView())
+        return;
+
+    // We don't want to hand off painting in the line box tree with the accumulated error of the render tree, as this will cause
+    // us to mess up painting aligned things (such as underlines in text) with both the render tree and line box tree's error.
+    LayoutPoint roundedPaintOffset = roundedIntPoint(paintOffset);
+    if (childrenInline())
+        m_lineBoxes.paint(this, paintInfo, roundedPaintOffset);
+    else
+        paintChildren(paintInfo, roundedPaintOffset);
+}
+
+void RenderBlock::paintChildren(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
+{
+    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 info(paintInfo);
+    info.phase = newPhase;
+    info.updatePaintingRootForChildren(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.
+    RenderView* renderView = view();
+    bool usePrintRect = !renderView->printRect().isEmpty();
+    
+    for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {        
+        // 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;
+        }
+
+        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())
+                    break;
+            }
+        }
+
+        LayoutPoint childPoint = flipForWritingModeForChild(child, paintOffset);
+        if (!child->hasSelfPaintingLayer() && !child->isFloating())
+            child->paint(info, 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;
+        }
+    }
+}
+
+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()->isContentEditable();
+    } 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())
+            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)
+        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(-layer()->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.context, 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;
+                }
+            }
+
+            if (!inlineEnclosedInSelfPaintingLayer)
+                cb->addContinuationWithOutline(inlineRenderer);
+            else if (!inlineRenderer->firstLineBox())
+                inlineRenderer->paintOutline(paintInfo.context, 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->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->m_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);
+            }
+        }
+    }
+}
+
+void RenderBlock::paintEllipsisBoxes(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
+{
+    if (!paintInfo.shouldPaintWithinRoot(this) || !firstLineBox())
+        return;
+
+    if (style()->visibility() == VISIBLE && paintInfo.phase == PaintPhaseForeground) {
+        // We can check the first box and last box and avoid painting if we don't
+        // intersect.
+        LayoutUnit yPos = paintOffset.y() + firstLineBox()->y();
+        LayoutUnit h = lastLineBox()->y() + lastLineBox()->logicalHeight() - firstLineBox()->y();
+        if (yPos >= paintInfo.rect.maxY() || yPos + h <= paintInfo.rect.y())
+            return;
+
+        // See if our boxes intersect with the dirty rect.  If so, then we paint
+        // them.  Note that boxes can easily overlap, so we can't make any assumptions
+        // based off positions of our first line box or our last line box.
+        for (RootInlineBox* curr = firstRootBox(); curr; curr = curr->nextRootBox()) {
+            yPos = paintOffset.y() + curr->y();
+            h = curr->logicalHeight();
+            if (curr->ellipsisBox() && yPos < paintInfo.rect.maxY() && yPos + h > paintInfo.rect.y())
+                curr->paintEllipsisBox(paintInfo, paintOffset, curr->lineTop(), curr->lineBottom());
+        }
+    }
+}
+
+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, 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;
+        
+    ListHashSet<RenderInline*>* continuations = table->get(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.context, accumulatedPaintOffset);
+    }
+    
+    // Delete
+    delete continuations;
+    table->remove(this);
+}
+
+bool RenderBlock::shouldPaintSelectionGaps() const
+{
+    return selectionState() != SelectionNone && style()->visibility() == VISIBLE && isSelectionRoot();
+}
+
+bool RenderBlock::isSelectionRoot() const
+{
+    if (!node())
+        return false;
+        
+    // 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() || isRelPositioned() ||
+        isFloatingOrPositioned() || isTableCell() || isInlineBlockOrInlineTable() || hasTransform() ||
+        hasReflection() || hasMask() || isWritingModeRoot())
+        return true;
+    
+    if (view() && view()->selectionStart()) {
+        Node* startElement = view()->selectionStart()->node();
+        if (startElement && startElement->rootEditableElement() == node())
+            return true;
+    }
+    
+    return false;
+}
+
+GapRects RenderBlock::selectionGapRectsForRepaint(RenderBoxModelObject* repaintContainer)
+{
+    ASSERT(!needsLayout());
+
+    if (!shouldPaintSelectionGaps())
+        return GapRects();
+
+    // FIXME: this is broken with transforms
+    TransformState transformState(TransformState::ApplyTransformDirection, FloatPoint());
+    mapLocalToContainer(repaintContainer, false, false, transformState);
+    LayoutPoint offsetFromRepaintContainer = roundedLayoutPoint(transformState.mappedPoint());
+
+    if (hasOverflowClip())
+        offsetFromRepaintContainer -= layer()->scrolledContentOffset();
+
+    LayoutUnit lastTop = 0;
+    LayoutUnit lastLeft = logicalLeftSelectionOffset(this, lastTop);
+    LayoutUnit lastRight = logicalRightSelectionOffset(this, lastTop);
+    
+    return selectionGaps(this, offsetFromRepaintContainer, IntSize(), lastTop, lastLeft, lastRight);
+}
+
+void RenderBlock::paintSelection(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
+{
+    if (shouldPaintSelectionGaps() && paintInfo.phase == PaintPhaseForeground) {
+        LayoutUnit lastTop = 0;
+        LayoutUnit lastLeft = logicalLeftSelectionOffset(this, lastTop);
+        LayoutUnit lastRight = logicalRightSelectionOffset(this, lastTop);
+        GraphicsContextStateSaver stateSaver(*paintInfo.context);
+
+        LayoutRect gapRectsBounds = selectionGaps(this, paintOffset, LayoutSize(), lastTop, lastLeft, lastRight, &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();
+                    gapRectsBounds.move(layer->scrolledContentOffset());
+                }
+                layer->addBlockSelectionGapsBounds(gapRectsBounds);
+            }
+        }
+    }
+}
+
+static void clipOutPositionedObjects(const PaintInfo* paintInfo, const LayoutPoint& offset, RenderBlock::PositionedObjectsListHashSet* positionedObjects)
+{
+    if (!positionedObjects)
+        return;
+    
+    RenderBlock::PositionedObjectsListHashSet::const_iterator end = positionedObjects->end();
+    for (RenderBlock::PositionedObjectsListHashSet::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 int blockDirectionOffset(RenderBlock* rootBlock, const LayoutSize& offsetFromRootBlock)
+{
+    return rootBlock->isHorizontalWritingMode() ? offsetFromRootBlock.height() : offsetFromRootBlock.width();
+}
+
+static int 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 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(), m_positionedObjects.get());
+        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->m_positionedObjects.get()); // 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(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());
+        lastLogicalRight = logicalRightSelectionOffset(rootBlock, logicalHeight());
+        return result;
+    }
+
+    if (childrenInline())
+        result = inlineSelectionGaps(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, lastLogicalTop, lastLogicalLeft, lastLogicalRight, paintInfo);
+    else
+        result = blockSelectionGaps(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, lastLogicalTop, lastLogicalLeft, lastLogicalRight, 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(), paintInfo));
+    return result;
+}
+
+GapRects RenderBlock::inlineSelectionGaps(RenderBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
+                                          LayoutUnit& lastLogicalTop, LayoutUnit& lastLogicalLeft, LayoutUnit& lastLogicalRight, 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());
+            lastLogicalRight = logicalRightSelectionOffset(rootBlock, logicalHeight());
+        }
+        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->selectionTop();
+        LayoutUnit selHeight = curr->selectionHeight();
+
+        if (!containsStart && !lastSelectedLine &&
+            selectionState() != SelectionStart && selectionState() != SelectionBoth)
+            result.uniteCenter(blockSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, lastLogicalTop, lastLogicalLeft, lastLogicalRight, 
+                                                 selTop, 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, 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());
+        lastLogicalRight = logicalRightSelectionOffset(rootBlock, lastSelectedLine->selectionBottom());
+    }
+    return result;
+}
+
+GapRects RenderBlock::blockSelectionGaps(RenderBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
+                                         LayoutUnit& lastLogicalTop, LayoutUnit& lastLogicalLeft, LayoutUnit& lastLogicalRight, 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()) { }
+
+    for (bool sawSelectionEnd = false; curr && !sawSelectionEnd; curr = curr->nextSiblingBox()) {
+        SelectionState childState = curr->selectionState();
+        if (childState == SelectionBoth || childState == SelectionEnd)
+            sawSelectionEnd = true;
+
+        if (curr->isFloatingOrPositioned())
+            continue; // We must be a normal flow object in order to even be considered.
+
+        if (curr->isRelPositioned() && 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()->relativePositionOffset();
+            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(), 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(), paintInfo));
+            if (rightGap)
+                result.uniteRight(logicalRightSelectionGap(rootBlock, rootBlockPhysicalPosition, offsetFromRootBlock, this, curr->logicalRight(), curr->logicalTop(), curr->logicalHeight(), 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());
+            lastLogicalRight = logicalRightSelectionOffset(rootBlock, curr->logicalBottom());
+        } 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, paintInfo));
+    }
+    return result;
+}
+
+LayoutRect RenderBlock::blockSelectionGap(RenderBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
+                                          LayoutUnit lastLogicalTop, LayoutUnit lastLogicalLeft, LayoutUnit lastLogicalRight, LayoutUnit logicalBottom, const PaintInfo* paintInfo)
+{
+    LayoutUnit logicalTop = lastLogicalTop;
+    LayoutUnit logicalHeight = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalBottom - logicalTop;
+    if (logicalHeight <= static_cast<LayoutUnit>(0))
+        return LayoutRect();
+
+    // Get the selection offsets for the bottom of the gap
+    LayoutUnit logicalLeft = max(lastLogicalLeft, logicalLeftSelectionOffset(rootBlock, logicalBottom));
+    LayoutUnit logicalRight = min(lastLogicalRight, logicalRightSelectionOffset(rootBlock, logicalBottom));
+    LayoutUnit logicalWidth = logicalRight - logicalLeft;
+    if (logicalWidth <= static_cast<LayoutUnit>(0))
+        return LayoutRect();
+
+    LayoutRect gapRect = rootBlock->logicalRectToPhysicalRect(rootBlockPhysicalPosition, LayoutRect(logicalLeft, logicalTop, logicalWidth, logicalHeight));
+    if (paintInfo)
+        paintInfo->context->fillRect(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 PaintInfo* paintInfo)
+{
+    LayoutUnit rootBlockLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalTop;
+    LayoutUnit rootBlockLogicalLeft = max(logicalLeftSelectionOffset(rootBlock, logicalTop), logicalLeftSelectionOffset(rootBlock, logicalTop + logicalHeight));
+    LayoutUnit rootBlockLogicalRight = min(inlineDirectionOffset(rootBlock, offsetFromRootBlock) + logicalLeft, min(logicalRightSelectionOffset(rootBlock, logicalTop), logicalRightSelectionOffset(rootBlock, logicalTop + logicalHeight)));
+    LayoutUnit rootBlockLogicalWidth = rootBlockLogicalRight - rootBlockLogicalLeft;
+    if (rootBlockLogicalWidth <= static_cast<LayoutUnit>(0))
+        return LayoutRect();
+
+    LayoutRect gapRect = rootBlock->logicalRectToPhysicalRect(rootBlockPhysicalPosition, LayoutRect(rootBlockLogicalLeft, rootBlockLogicalTop, rootBlockLogicalWidth, logicalHeight));
+    if (paintInfo)
+        paintInfo->context->fillRect(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 PaintInfo* paintInfo)
+{
+    LayoutUnit rootBlockLogicalTop = blockDirectionOffset(rootBlock, offsetFromRootBlock) + logicalTop;
+    LayoutUnit rootBlockLogicalLeft = max(inlineDirectionOffset(rootBlock, offsetFromRootBlock) + logicalRight, max(logicalLeftSelectionOffset(rootBlock, logicalTop), logicalLeftSelectionOffset(rootBlock, logicalTop + logicalHeight)));
+    LayoutUnit rootBlockLogicalRight = min(logicalRightSelectionOffset(rootBlock, logicalTop), logicalRightSelectionOffset(rootBlock, logicalTop + logicalHeight));
+    LayoutUnit rootBlockLogicalWidth = rootBlockLogicalRight - rootBlockLogicalLeft;
+    if (rootBlockLogicalWidth <= static_cast<LayoutUnit>(0))
+        return LayoutRect();
+
+    LayoutRect gapRect = rootBlock->logicalRectToPhysicalRect(rootBlockPhysicalPosition, LayoutRect(rootBlockLogicalLeft, rootBlockLogicalTop, rootBlockLogicalWidth, logicalHeight));
+    if (paintInfo)
+        paintInfo->context->fillRect(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)
+{
+    LayoutUnit logicalLeft = logicalLeftOffsetForLine(position, false);
+    if (logicalLeft == logicalLeftOffsetForContent()) {
+        if (rootBlock != this)
+            // The border can potentially be further extended by our containingBlock().
+            return containingBlock()->logicalLeftSelectionOffset(rootBlock, position + logicalTop());
+        return logicalLeft;
+    } else {
+        RenderBlock* cb = this;
+        while (cb != rootBlock) {
+            logicalLeft += cb->logicalLeft();
+            cb = cb->containingBlock();
+        }
+    }
+    return logicalLeft;
+}
+
+LayoutUnit RenderBlock::logicalRightSelectionOffset(RenderBlock* rootBlock, LayoutUnit position)
+{
+    LayoutUnit logicalRight = logicalRightOffsetForLine(position, false);
+    if (logicalRight == logicalRightOffsetForContent()) {
+        if (rootBlock != this)
+            // The border can potentially be further extended by our containingBlock().
+            return containingBlock()->logicalRightSelectionOffset(rootBlock, position + logicalTop());
+        return logicalRight;
+    } else {
+        RenderBlock* cb = this;
+        while (cb != rootBlock) {
+            logicalRight += cb->logicalLeft();
+            cb = cb->containingBlock();
+        }
+    }
+    return logicalRight;
+}
+
+void RenderBlock::insertPositionedObject(RenderBox* o)
+{
+    ASSERT(!isAnonymousBlock());
+
+    if (o->isRenderFlowThread())
+        return;
+    
+    // Create the list of special objects if we don't aleady have one
+    if (!m_positionedObjects)
+        m_positionedObjects = adoptPtr(new PositionedObjectsListHashSet);
+
+    m_positionedObjects->add(o);
+}
+
+void RenderBlock::removePositionedObject(RenderBox* o)
+{
+    if (m_positionedObjects)
+        m_positionedObjects->remove(o);
+}
+
+void RenderBlock::removePositionedObjects(RenderBlock* o)
+{
+    if (!m_positionedObjects)
+        return;
+    
+    RenderBox* r;
+    
+    Iterator end = m_positionedObjects->end();
+    
+    Vector<RenderBox*, 16> deadObjects;
+
+    for (Iterator it = m_positionedObjects->begin(); it != end; ++it) {
+        r = *it;
+        if (!o || r->isDescendantOf(o)) {
+            if (o)
+                r->setChildNeedsLayout(true, false);
+            
+            // 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++)
+        m_positionedObjects->remove(deadObjects.at(i));
+}
+
+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)
+        m_floatingObjects = adoptPtr(new FloatingObjects(this, isHorizontalWritingMode()));
+    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.
+    if (!o->isPositioned()) {
+        bool isChildRenderBlock = o->isRenderBlock();
+        if (isChildRenderBlock && !o->needsLayout() && view()->layoutState()->pageLogicalHeightChanged())
+            o->setChildNeedsLayout(true, false);
+            
+        bool affectedByPagination = isChildRenderBlock && view()->layoutState()->m_pageLogicalHeight;
+        if (!affectedByPagination || isWritingModeRoot()) // We are unsplittable if we're a block flow root.
+            o->layoutIfNeeded();
+        else {
+            o->computeLogicalWidth();
+            o->computeBlockDirectionMargins(this);
+        }
+    }
+    setLogicalWidthForFloat(newObj, logicalWidthForChild(o) + marginStartForChild(o) + marginEndForChild(o));
+
+    newObj->m_shouldPaint = !o->hasSelfPaintingLayer(); // If a layer exists, the float will paint itself.  Otherwise someone else will.
+    newObj->m_isDescendant = 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 == numeric_limits<LayoutUnit>::max())
+                    logicalBottom = numeric_limits<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)
+{
+    if (!m_floatingObjects)
+        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();
+    }
+}
+
+LayoutPoint RenderBlock::computeLogicalLocationForFloat(const FloatingObject* floatingObject, LayoutUnit logicalTopOffset) const
+{
+    RenderBox* childBox = floatingObject->renderer();
+    LayoutUnit logicalRightOffset = logicalRightOffsetForContent(logicalTopOffset); // Constant part of right offset.
+    LayoutUnit logicalLeftOffset = logicalLeftOffsetForContent(logicalTopOffset); // Constant part of left offset.
+    LayoutUnit floatLogicalWidth = min(logicalWidthForFloat(floatingObject), logicalRightOffset - logicalLeftOffset); // The width we look for.
+
+    LayoutUnit floatLogicalLeft;
+
+    if (childBox->style()->floating() == LeftFloat) {
+        LayoutUnit heightRemainingLeft = 1;
+        LayoutUnit heightRemainingRight = 1;
+        floatLogicalLeft = logicalLeftOffsetForLine(logicalTopOffset, logicalLeftOffset, false, &heightRemainingLeft);
+        while (logicalRightOffsetForLine(logicalTopOffset, logicalRightOffset, false, &heightRemainingRight) - floatLogicalLeft < floatLogicalWidth) {
+            logicalTopOffset += min(heightRemainingLeft, heightRemainingRight);
+            floatLogicalLeft = logicalLeftOffsetForLine(logicalTopOffset, logicalLeftOffset, false, &heightRemainingLeft);
+            if (inRenderFlowThread()) {
+                // 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<LayoutUnit>(logicalLeftOffset - borderAndPaddingLogicalLeft(), floatLogicalLeft);
+    } else {
+        LayoutUnit heightRemainingLeft = 1;
+        LayoutUnit heightRemainingRight = 1;
+        floatLogicalLeft = logicalRightOffsetForLine(logicalTopOffset, logicalRightOffset, false, &heightRemainingRight);
+        while (floatLogicalLeft - logicalLeftOffsetForLine(logicalTopOffset, logicalLeftOffset, false, &heightRemainingLeft) < floatLogicalWidth) {
+            logicalTopOffset += min(heightRemainingLeft, heightRemainingRight);
+            floatLogicalLeft = logicalRightOffsetForLine(logicalTopOffset, logicalRightOffset, false, &heightRemainingRight);
+            if (inRenderFlowThread()) {
+                // 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.
+    }
+    
+    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;
+        }
+    }
+
+    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. Also don't attempt to handle
+        // positioned floats, since the positioning layout code handles those.
+        if (floatingObject->renderer()->containingBlock() != this || floatingObject->renderer()->isPositioned())
+            continue;
+
+        RenderBox* childBox = floatingObject->renderer();
+        LayoutUnit childLogicalLeftMargin = style()->isLeftToRightDirection() ? marginStartForChild(childBox) : marginEndForChild(childBox);
+
+        LayoutRect oldRect(childBox->x(), childBox->y() , childBox->width(), childBox->height());
+
+        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));
+
+        if (view()->layoutState()->isPaginated()) {
+            RenderBlock* childBlock = childBox->isRenderBlock() ? toRenderBlock(childBox) : 0;
+
+            if (!childBox->needsLayout())
+                childBox->markForPaginationRelayoutIfNeeded();
+            childBox->layoutIfNeeded();
+
+            // 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.
+            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, false);
+                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
+    int 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)
+{
+    if (!gPercentHeightDescendantsMap) {
+        gPercentHeightDescendantsMap = new PercentHeightDescendantsMap;
+        gPercentHeightContainerMap = new PercentHeightContainerMap;
+    }
+
+    HashSet<RenderBox*>* descendantSet = gPercentHeightDescendantsMap->get(this);
+    if (!descendantSet) {
+        descendantSet = new HashSet<RenderBox*>;
+        gPercentHeightDescendantsMap->set(this, descendantSet);
+    }
+    bool added = descendantSet->add(descendant).second;
+    if (!added) {
+        ASSERT(gPercentHeightContainerMap->get(descendant));
+        ASSERT(gPercentHeightContainerMap->get(descendant)->contains(this));
+        return;
+    }
+
+    HashSet<RenderBlock*>* containerSet = gPercentHeightContainerMap->get(descendant);
+    if (!containerSet) {
+        containerSet = new HashSet<RenderBlock*>;
+        gPercentHeightContainerMap->set(descendant, containerSet);
+    }
+    ASSERT(!containerSet->contains(this));
+    containerSet->add(this);
+}
+
+void RenderBlock::removePercentHeightDescendant(RenderBox* descendant)
+{
+    if (!gPercentHeightContainerMap)
+        return;
+
+    HashSet<RenderBlock*>* containerSet = gPercentHeightContainerMap->take(descendant);
+    if (!containerSet)
+        return;
+
+    HashSet<RenderBlock*>::iterator end = containerSet->end();
+    for (HashSet<RenderBlock*>::iterator it = containerSet->begin(); it != end; ++it) {
+        RenderBlock* container = *it;
+        HashSet<RenderBox*>* descendantSet = gPercentHeightDescendantsMap->get(container);
+        ASSERT(descendantSet);
+        if (!descendantSet)
+            continue;
+        ASSERT(descendantSet->contains(descendant));
+        descendantSet->remove(descendant);
+        if (descendantSet->isEmpty()) {
+            gPercentHeightDescendantsMap->remove(container);
+            delete descendantSet;
+        }
+    }
+
+    delete containerSet;
+}
+
+HashSet<RenderBox*>* RenderBlock::percentHeightDescendants() const
+{
+    return gPercentHeightDescendantsMap ? gPercentHeightDescendantsMap->get(this) : 0;
+}
+
+#if !ASSERT_DISABLED
+bool RenderBlock::hasPercentHeightDescendant(RenderBox* descendant)
+{
+    ASSERT(descendant);
+    if (!gPercentHeightContainerMap)
+        return false;
+    HashSet<RenderBlock*>* containerSet = gPercentHeightContainerMap->take(descendant);
+    return containerSet && containerSet->size();
+}
+#endif
+
+template <RenderBlock::FloatingObject::Type FloatTypeValue>
+inline void RenderBlock::FloatIntervalSearchAdapter<FloatTypeValue>::collectIfNeeded(const IntervalType& interval) const
+{
+    const FloatingObject* r = interval.data();
+    if (r->type() == FloatTypeValue && interval.low() <= m_value && m_value < interval.high()) {
+        // All the objects returned from the tree should be already placed.
+        ASSERT(r->isPlaced() && m_renderer->logicalTopForFloat(r) <= m_value && m_renderer->logicalBottomForFloat(r) > m_value);
+
+        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_value;
+        }
+
+        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_value;
+        }
+    }
+}
+
+LayoutUnit RenderBlock::textIndentOffset() const
+{
+    LayoutUnit cw = 0;
+    if (style()->textIndent().isPercent())
+        cw = containingBlock()->availableLogicalWidth();
+    return style()->textIndent().calcMinValue(cw);
+}
+
+LayoutUnit RenderBlock::logicalLeftOffsetForContent(RenderRegion* region, LayoutUnit offsetFromLogicalTopOfFirstPage) const
+{
+    LayoutUnit logicalLeftOffset = style()->isHorizontalWritingMode() ? borderLeft() + paddingLeft() : borderTop() + paddingTop();
+    if (!inRenderFlowThread())
+        return logicalLeftOffset;
+    LayoutRect boxRect = borderBoxRectInRegion(region, offsetFromLogicalTopOfFirstPage);
+    return logicalLeftOffset + (isHorizontalWritingMode() ? boxRect.x() : boxRect.y());
+}
+
+LayoutUnit RenderBlock::logicalRightOffsetForContent(RenderRegion* region, LayoutUnit offsetFromLogicalTopOfFirstPage) const
+{
+    LayoutUnit logicalRightOffset = style()->isHorizontalWritingMode() ? borderLeft() + paddingLeft() : borderTop() + paddingTop();
+    logicalRightOffset += availableLogicalWidth();
+    if (!inRenderFlowThread())
+        return logicalRightOffset;
+    LayoutRect boxRect = borderBoxRectInRegion(region, offsetFromLogicalTopOfFirstPage);
+    return logicalRightOffset - (logicalWidth() - (isHorizontalWritingMode() ? boxRect.maxX() : boxRect.maxY()));
+}
+
+LayoutUnit RenderBlock::logicalLeftOffsetForLine(LayoutUnit logicalTop, LayoutUnit fixedOffset, bool applyTextIndent, LayoutUnit* heightRemaining) const
+{
+    LayoutUnit left = fixedOffset;
+    if (m_floatingObjects && m_floatingObjects->hasLeftObjects()) {
+        if (heightRemaining)
+            *heightRemaining = 1;
+
+        FloatIntervalSearchAdapter<FloatingObject::FloatLeft> adapter(this, logicalTop, left, heightRemaining);
+        m_floatingObjects->placedFloatsTree().allOverlapsWithAdapter(adapter);
+    }
+
+    if (applyTextIndent && style()->isLeftToRightDirection())
+        left += textIndentOffset();
+
+    return left;
+}
+
+LayoutUnit RenderBlock::logicalRightOffsetForLine(LayoutUnit logicalTop, LayoutUnit fixedOffset, bool applyTextIndent, LayoutUnit* heightRemaining) const
+{
+    LayoutUnit right = fixedOffset;
+    if (m_floatingObjects && m_floatingObjects->hasRightObjects()) {
+        if (heightRemaining)
+            *heightRemaining = 1;
+
+        LayoutUnit rightFloatOffset = fixedOffset;
+        FloatIntervalSearchAdapter<FloatingObject::FloatRight> adapter(this, logicalTop, rightFloatOffset, heightRemaining);
+        m_floatingObjects->placedFloatsTree().allOverlapsWithAdapter(adapter);
+        right = min(right, rightFloatOffset);
+    }
+    
+    if (applyTextIndent && !style()->isLeftToRightDirection())
+        right -= textIndentOffset();
+    
+    return right;
+}
+
+LayoutUnit RenderBlock::nextFloatLogicalBottomBelow(LayoutUnit logicalHeight) const
+{
+    if (!m_floatingObjects)
+        return logicalHeight;
+
+    LayoutUnit bottom = numeric_limits<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 == numeric_limits<LayoutUnit>::max() ? 0 : bottom;
+}
+
+LayoutUnit RenderBlock::lowestFloatLogicalBottom(FloatingObject::Type floatType) const
+{
+    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;
+}
+
+void RenderBlock::markLinesDirtyInBlockRange(LayoutUnit logicalTop, LayoutUnit logicalBottom, RootInlineBox* highest)
+{
+    if (logicalTop >= logicalBottom)
+        return;
+
+    RootInlineBox* lowestDirtyLine = lastRootBox();
+    RootInlineBox* afterLowest = lowestDirtyLine;
+    while (lowestDirtyLine && lowestDirtyLine->lineBottomWithLeading() >= logicalBottom && logicalBottom < numeric_limits<LayoutUnit>::max()) {
+        afterLowest = lowestDirtyLine;
+        lowestDirtyLine = lowestDirtyLine->prevRootBox();
+    }
+
+    while (afterLowest && afterLowest != highest && (afterLowest->lineBottomWithLeading() >= logicalTop || afterLowest->lineBottomWithLeading() < 0)) {
+        afterLowest->markDirty();
+        afterLowest = afterLowest->prevRootBox();
+    }
+}
+
+void RenderBlock::addPositionedFloats()
+{
+    if (!m_positionedObjects)
+        return;
+    
+    Iterator end = m_positionedObjects->end();
+    for (Iterator it = m_positionedObjects->begin(); it != end; ++it) {
+        RenderBox* positionedObject = *it;
+        if (!positionedObject->isFloating())
+            continue;
+
+        ASSERT(!positionedObject->needsLayout());
+
+        // If we're a positioned float, then we need to insert ourselves as a floating object also. We only do
+        // this after the positioned object has received a layout, since otherwise the dimensions and placement
+        // won't be correct.
+        FloatingObject* floatingObject = insertFloatingObject(positionedObject);
+        setLogicalLeftForFloat(floatingObject, logicalLeftForChild(positionedObject) - marginLogicalLeftForChild(positionedObject));
+        setLogicalTopForFloat(floatingObject, logicalTopForChild(positionedObject) - marginBeforeForChild(positionedObject));
+        setLogicalHeightForFloat(floatingObject, logicalHeightForChild(positionedObject) + marginBeforeForChild(positionedObject) + marginAfterForChild(positionedObject));
+
+        m_floatingObjects->addPlacedObject(floatingObject);
+        
+        m_hasPositionedFloats = true;
+    }
+}
+
+void RenderBlock::clearFloats(BlockLayoutPass layoutPass)
+{
+    if (m_floatingObjects)
+        m_floatingObjects->setHorizontalWritingMode(isHorizontalWritingMode());
+
+    // Clear our positioned floats boolean.
+    m_hasPositionedFloats = false;
+
+    // Inline blocks are covered by the isReplaced() check in the avoidFloats method.
+    if (avoidsFloats() || isRoot() || isRenderView() || isFloatingOrPositioned() || isTableCell()) {
+        if (m_floatingObjects) {
+            deleteAllValues(m_floatingObjects->set());
+            m_floatingObjects->clear();
+        }
+        if (layoutPass == PositionedFloatLayoutPass)
+            addPositionedFloats();
+        return;
+    }
+
+    typedef HashMap<RenderObject*, FloatingObject*> RendererToFloatInfoMap;
+    RendererToFloatInfoMap floatMap;
+
+    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();
+    }
+
+    if (layoutPass == PositionedFloatLayoutPass)
+        addPositionedFloats();
+
+    // 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;
+
+    // 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 = parentBlock->hasPositionedFloats();
+    RenderObject* prev = previousSibling();
+    while (prev && (prev->isFloatingOrPositioned() || !prev->isBox() || !prev->isRenderBlock() || toRenderBlock(prev)->avoidsFloats())) {
+        if (prev->isFloating())
+            parentHasFloats = true;
+        prev = prev->previousSibling();
+    }
+
+    // First add in floats from the parent.
+    LayoutUnit logicalTopOffset = logicalTop();
+    if (parentHasFloats)
+        addIntrudingFloats(parentBlock, parentBlock->logicalLeftOffsetForContent(), logicalTopOffset);
+    
+    LayoutUnit logicalLeftOffset = 0;
+    if (prev)
+        logicalTopOffset -= toRenderBox(prev)->logicalTop();
+    else if (!parentHasFloats) {
+        prev = parentBlock;
+        logicalLeftOffset += parentBlock->logicalLeftOffsetForContent();
+    }
+
+    // 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 && block->m_floatingObjects && block->lowestFloatLogicalBottomIncludingPositionedFloats() > logicalTopOffset)
+        addIntrudingFloats(block, logicalLeftOffset, logicalTopOffset);
+
+    if (childrenInline()) {
+        LayoutUnit changeLogicalTop = numeric_limits<LayoutUnit>::max();
+        LayoutUnit changeLogicalBottom = numeric_limits<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));
+                    }
+
+                    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);
+                }
+            }
+        }
+
+        RendererToFloatInfoMap::iterator end = floatMap.end();
+        for (RendererToFloatInfoMap::iterator it = floatMap.begin(); it != end; ++it) {
+            FloatingObject* floatingObject = (*it).second;
+            if (!floatingObject->m_isDescendant) {
+                changeLogicalTop = 0;
+                changeLogicalBottom = max(changeLogicalBottom, logicalBottomForFloat(floatingObject));
+            }
+        }
+        deleteAllValues(floatMap);
+
+        markLinesDirtyInBlockRange(changeLogicalTop, changeLogicalBottom);
+    }
+}
+
+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;
+
+    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), numeric_limits<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)) {
+                LayoutUnit leftOffset = isHorizontalWritingMode() ? -childLogicalLeft : -childLogicalTop;
+                LayoutUnit topOffset = isHorizontalWritingMode() ? -childLogicalTop : -childLogicalLeft;
+                FloatingObject* floatingObj = new FloatingObject(r->type(), LayoutRect(r->x() - leftOffset, r->y() - topOffset, r->width(), r->height()));
+                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->m_shouldPaint = false;
+                else
+                    floatingObj->m_shouldPaint = false;
+                
+                floatingObj->m_isDescendant = true;
+
+                // We create the floating object list lazily.
+                if (!m_floatingObjects)
+                    m_floatingObjects = adoptPtr(new FloatingObjects(this, isHorizontalWritingMode()));
+
+                m_floatingObjects->add(floatingObj);
+            }
+        } else {
+            if (makeChildPaintOtherFloats && !r->m_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->m_shouldPaint = 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->m_isDescendant)
+                child->addOverflowFromChild(r->m_renderer, LayoutSize(xPositionForFloatIncludingMargin(r), yPositionForFloatIncludingMargin(r)));
+        }
+    }
+    return lowestFloatLogicalBottom;
+}
+
+bool RenderBlock::hasOverhangingFloat(RenderBox* renderer)
+{
+    if (!m_floatingObjects || hasColumns() || !parent())
+        return false;
+
+    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
+    FloatingObjectSetIterator it = floatingObjectSet.find<RenderBox*, FloatingObjectHashTranslator>(renderer);
+    if (it == floatingObjectSet.end())
+        return false;
+
+    return logicalBottomForFloat(*it) > logicalHeight();
+}
+
+void RenderBlock::addIntrudingFloats(RenderBlock* prev, LayoutUnit logicalLeftOffset, LayoutUnit logicalTopOffset)
+{
+    // If the parent or previous sibling doesn't have any floats to add, don't bother.
+    if (!prev->m_floatingObjects)
+        return;
+
+    logicalLeftOffset += (isHorizontalWritingMode() ? marginLeft() : marginTop());
+
+    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)) {
+                LayoutUnit leftOffset = isHorizontalWritingMode() ? logicalLeftOffset : logicalTopOffset;
+                LayoutUnit topOffset = isHorizontalWritingMode() ? logicalTopOffset : logicalLeftOffset;
+                
+                FloatingObject* floatingObj = new FloatingObject(r->type(), LayoutRect(r->x() - leftOffset, r->y() - topOffset, r->width(), r->height()));
+
+                // 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->m_shouldPaint = 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)
+                    m_floatingObjects = adoptPtr(new FloatingObjects(this, isHorizontalWritingMode()));
+                m_floatingObjects->add(floatingObj);
+            }
+        }
+    }
+}
+
+bool RenderBlock::avoidsFloats() const
+{
+    // Floats can't intrude into our box if we have a non-auto column count or width.
+    return RenderBox::avoidsFloats() || !style()->hasAutoColumnCount() || !style()->hasAutoColumnWidth();
+}
+
+bool RenderBlock::containsFloat(RenderBox* renderer)
+{
+    return m_floatingObjects && m_floatingObjects->set().contains<RenderBox*, FloatingObjectHashTranslator>(renderer);
+}
+
+void RenderBlock::markAllDescendantsWithFloatsForLayout(RenderBox* floatToRemove, bool inLayout)
+{
+    if (!everHadLayout())
+        return;
+
+    setChildNeedsLayout(true, !inLayout);
+ 
+    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->isFloatingOrPositioned()) || !child->isRenderBlock())
+                continue;
+            RenderBlock* childBlock = toRenderBlock(child);
+            if ((floatToRemove ? childBlock->containsFloat(floatToRemove) : childBlock->containsFloats()) || childBlock->shrinkToAvoidFloats())
+                childBlock->markAllDescendantsWithFloatsForLayout(floatToRemove, inLayout);
+        }
+    }
+}
+
+void RenderBlock::markSiblingsWithFloatsForLayout()
+{
+    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
+    FloatingObjectSetIterator end = floatingObjectSet.end();
+    for (FloatingObjectSetIterator it = floatingObjectSet.begin(); it != end; ++it) {
+        if (logicalBottomForFloat(*it) > logicalHeight()) {
+            RenderBox* floatingBox = (*it)->renderer();
+
+            RenderObject* next = nextSibling();
+            while (next) {
+                if (next->isRenderBlock() && !next->isFloatingOrPositioned() && !toRenderBlock(next)->avoidsFloats()) {
+                    RenderBlock* nextBlock = toRenderBlock(next);
+                    if (nextBlock->containsFloat(floatingBox))
+                        nextBlock->markAllDescendantsWithFloatsForLayout(floatingBox);
+                    else
+                        break;
+                }
+
+                next = next->nextSibling();
+            }
+        }
+    }
+}
+
+LayoutUnit RenderBlock::getClearDelta(RenderBox* child, LayoutUnit logicalTop)
+{
+    // 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;
+    }
+
+    // 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) : 0;
+    if (!result && child->avoidsFloats()) {
+        LayoutUnit newLogicalTop = logicalTop;
+        while (true) {
+            LayoutUnit availableLogicalWidthAtNewLogicalTopOffset = availableLogicalWidthForLine(newLogicalTop, false);
+            // FIXME: Change to use roughlyEquals when we move to float.
+            // See https://bugs.webkit.org/show_bug.cgi?id=66148
+            if (availableLogicalWidthAtNewLogicalTopOffset == availableLogicalWidthForContent(newLogicalTop))
+                return newLogicalTop - logicalTop;
+
+            // 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->computeLogicalWidth();
+            RenderRegion* region = regionAtBlockOffset(logicalTopForChild(child));
+            LayoutRect borderBox = child->borderBoxRectInRegion(region, offsetFromLogicalTopOfFirstPage() + logicalTopForChild(child), DoNotCacheRenderBoxRegionInfo);
+            LayoutUnit childLogicalWidthAtNewLogicalTopOffset = isHorizontalWritingMode() ? borderBox.width() : borderBox.height();
+
+            child->setLogicalTop(childOldLogicalTop);
+            child->setLogicalWidth(childOldLogicalWidth);
+            child->setMarginLeft(childOldMarginLeft);
+            child->setMarginRight(childOldMarginRight);
+            
+            // FIXME: Change to use roughlyEquals when we move to float.
+            // See https://bugs.webkit.org/show_bug.cgi?id=66148
+            if (childLogicalWidthAtNewLogicalTopOffset <= availableLogicalWidthAtNewLogicalTopOffset)
+                return newLogicalTop - logicalTop;
+
+            newLogicalTop = nextFloatLogicalBottomBelow(newLogicalTop);
+            ASSERT(newLogicalTop >= logicalTop);
+            if (newLogicalTop < logicalTop)
+                break;
+        }
+        ASSERT_NOT_REACHED();
+    }
+    return result;
+}
+
+bool RenderBlock::isPointInOverflowControl(HitTestResult& result, const LayoutPoint& pointInContainer, const LayoutPoint& accumulatedOffset)
+{
+    if (!scrollsOverflow())
+        return false;
+
+    return layer()->hitTestOverflowControls(result, pointInContainer - toLayoutSize(accumulatedOffset));
+}
+
+bool RenderBlock::nodeAtPoint(const HitTestRequest& request, HitTestResult& result, const LayoutPoint& pointInContainer, const LayoutPoint& accumulatedOffset, HitTestAction hitTestAction)
+{
+    LayoutPoint adjustedLocation(accumulatedOffset + location());
+    LayoutSize localOffset = toLayoutSize(adjustedLocation);
+
+    if (!isRenderView()) {
+        // Check if we need to do anything at all.
+        LayoutRect overflowBox = visualOverflowRect();
+        flipForWritingMode(overflowBox);
+        overflowBox.moveBy(adjustedLocation);
+        if (!overflowBox.intersects(result.rectForPoint(pointInContainer)))
+            return false;
+    }
+
+    if ((hitTestAction == HitTestBlockBackground || hitTestAction == HitTestChildBlockBackground) && isPointInOverflowControl(result, pointInContainer, adjustedLocation)) {
+        updateHitTestResult(result, pointInContainer - localOffset);
+        // FIXME: isPointInOverflowControl() doesn't handle rect-based tests yet.
+        if (!result.addNodeToRectBasedTestResult(node(), pointInContainer))
+           return true;
+    }
+
+    // If we have clipping, then we can't have any spillout.
+    bool useOverflowClip = hasOverflowClip() && !hasSelfPaintingLayer();
+    bool useClip = (hasControlClip() || useOverflowClip);
+    LayoutRect hitTestArea(result.rectForPoint(pointInContainer));
+    bool checkChildren = !useClip || (hasControlClip() ? controlClipRect(adjustedLocation).intersects(hitTestArea) : overflowClipRect(adjustedLocation, result.region(), IncludeOverlayScrollbarSize).intersects(hitTestArea));
+    if (checkChildren) {
+        // Hit test descendants first.
+        LayoutSize scrolledOffset(localOffset);
+        if (hasOverflowClip()) {
+            scrolledOffset -= layer()->scrolledContentOffset();
+        }
+
+        // Hit test contents if we don't have columns.
+        if (!hasColumns()) {
+            if (hitTestContents(request, result, pointInContainer, toLayoutPoint(scrolledOffset), hitTestAction)) {
+                updateHitTestResult(result, pointInContainer - localOffset);
+                return true;
+            }
+            if (hitTestAction == HitTestFloat && hitTestFloats(request, result, pointInContainer, toLayoutPoint(scrolledOffset)))
+                return true;
+        } else if (hitTestColumns(request, result, pointInContainer, toLayoutPoint(scrolledOffset), hitTestAction)) {
+            updateHitTestResult(result, flipForWritingMode(pointInContainer - localOffset));
+            return true;
+        }
+    }
+
+    // Now hit test our background
+    if (hitTestAction == HitTestBlockBackground || hitTestAction == HitTestChildBlockBackground) {
+        LayoutRect boundsRect(adjustedLocation, size());
+        if (visibleToHitTesting() && boundsRect.intersects(result.rectForPoint(pointInContainer))) {
+            updateHitTestResult(result, flipForWritingMode(pointInContainer - localOffset));
+            if (!result.addNodeToRectBasedTestResult(node(), pointInContainer, boundsRect))
+                return true;
+        }
+    }
+
+    return false;
+}
+
+bool RenderBlock::hitTestFloats(const HitTestRequest& request, HitTestResult& result, const LayoutPoint& pointInContainer, const LayoutPoint& accumulatedOffset)
+{
+    if (!m_floatingObjects)
+        return false;
+
+    LayoutPoint adjustedLocation = accumulatedOffset;
+    if (isRenderView()) {
+        adjustedLocation += toLayoutSize(toRenderView(this)->frameView()->scrollPosition());
+    }
+
+    const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
+    FloatingObjectSetIterator begin = floatingObjectSet.begin();
+    for (FloatingObjectSetIterator it = floatingObjectSet.end(); it != begin;) {
+        --it;
+        FloatingObject* floatingObject = *it;
+        if (floatingObject->m_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, pointInContainer, childPoint)) {
+                updateHitTestResult(result, pointInContainer - toLayoutSize(childPoint));
+                return true;
+            }
+        }
+    }
+
+    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 = colCount * m_colInfo->columnHeight() * m_direction;
+        update();
+    }
+
+    void advance()
+    {
+        ASSERT(hasMore());
+        m_colIndex--;
+        update();
+    }
+
+    LayoutRect columnRect() const { return m_colRect; }
+    bool hasMore() const { return m_colIndex >= 0; }
+
+    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);
+        if (m_colInfo->progressionAxis() == ColumnInfo::BlockAxis) {
+            if (m_isHorizontal)
+                offset.expand(0, m_colRect.y() - m_block.borderTop() - m_block.paddingTop());
+            else
+                offset.expand(m_colRect.x() - m_block.borderLeft() - m_block.paddingLeft(), 0);
+        }
+    }
+
+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_isHorizontal ? m_colRect.height() : m_colRect.width()) * m_direction;
+    }
+
+    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;
+};
+
+bool RenderBlock::hitTestColumns(const HitTestRequest& request, HitTestResult& result, const LayoutPoint& pointInContainer, const LayoutPoint& accumulatedOffset, HitTestAction hitTestAction)
+{
+    // We need to do multiple passes, breaking up our hit testing into strips.
+    if (!hasColumns())
+        return false;
+
+    for (ColumnRectIterator it(*this); it.hasMore(); it.advance()) {
+        LayoutRect hitRect = result.rectForPoint(pointInContainer);
+        LayoutRect colRect = it.columnRect();
+        colRect.moveBy(accumulatedOffset);
+        if (colRect.intersects(hitRect)) {
+            // 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, pointInContainer, finalLocation, hitTestAction) || (hitTestAction == HitTestFloat && hitTestFloats(request, result, pointInContainer, finalLocation));
+
+            hitTestContents(request, result, pointInContainer, finalLocation, hitTestAction);
+        }
+    }
+
+    return false;
+}
+
+void RenderBlock::adjustForColumnRect(LayoutSize& offset, const LayoutPoint& pointInContainer) const
+{
+    for (ColumnRectIterator it(*this); it.hasMore(); it.advance()) {
+        LayoutRect colRect = it.columnRect();
+        if (colRect.contains(pointInContainer)) {
+            it.adjust(offset);
+            return;
+        }
+    }
+}
+
+bool RenderBlock::hitTestContents(const HitTestRequest& request, HitTestResult& result, const LayoutPoint& pointInContainer, const LayoutPoint& accumulatedOffset, HitTestAction hitTestAction)
+{
+    if (childrenInline() && !isTable()) {
+        // We have to hit-test our line boxes.
+        if (m_lineBoxes.hitTest(this, request, result, pointInContainer, 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, pointInContainer, childPoint, childHitTest))
+                return true;
+        }
+    }
+    
+    return false;
+}
+
+Position RenderBlock::positionForBox(InlineBox *box, bool start) const
+{
+    if (!box)
+        return Position();
+
+    if (!box->renderer()->node())
+        return createLegacyEditingPosition(node(), start ? caretMinOffset() : caretMaxOffset());
+
+    if (!box->isInlineTextBox())
+        return createLegacyEditingPosition(box->renderer()->node(), start ? box->renderer()->caretMinOffset() : box->renderer()->caretMaxOffset());
+
+    InlineTextBox* textBox = toInlineTextBox(box);
+    return createLegacyEditingPosition(box->renderer()->node(), start ? textBox->start() : textBox->start() + textBox->len());
+}
+
+static inline bool isEditingBoundary(RenderObject* ancestor, RenderObject* child)
+{
+    ASSERT(!ancestor || ancestor->node());
+    ASSERT(child && child->node());
+    return !ancestor || !ancestor->parent() || (ancestor->hasLayer() && ancestor->parent()->isRenderView())
+        || ancestor->node()->rendererIsEditable() == child->node()->rendererIsEditable();
+}
+
+// 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)
+{
+    LayoutPoint childLocation = child->location();
+    if (child->isRelPositioned())
+        childLocation += child->relativePositionOffset();
+    // 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->node();
+    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->node())
+        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);
+
+    // 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);
+}
+
+VisiblePosition RenderBlock::positionForPointWithInlineChildren(const LayoutPoint& pointInLogicalContents)
+{
+    ASSERT(childrenInline());
+
+    if (!firstRootBox())
+        return createVisiblePosition(0, DOWNSTREAM);
+
+    // 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())
+            continue;
+        if (!firstRootBoxWithChildren)
+            firstRootBoxWithChildren = root;
+        lastRootBoxWithChildren = root;
+
+        // check if this root line box is located at this y coordinate
+        if (pointInLogicalContents.y() < root->selectionBottom()) {
+            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 && pointInLogicalContents.y() < firstRootBoxWithChildren->selectionTop()
+            && pointInLogicalContents.y() < firstRootBoxWithChildren->logicalTop()) {
+            // y coordinate is above first root line box, so return the start of the first
+            return VisiblePosition(positionForBox(firstRootBoxWithChildren->firstLeafChild(), true), DOWNSTREAM);
+        }
+
+        // pass the box a top position that is inside it
+        LayoutPoint point(pointInLogicalContents.x(), closestBox->logicalTop());
+        if (!isHorizontalWritingMode())
+            point = point.transposedPoint();
+        if (closestBox->renderer()->isReplaced())
+            return positionForPointRespectingEditingBoundaries(this, toRenderBox(closestBox->renderer()), point);
+        return closestBox->renderer()->positionForPoint(point);
+    }
+
+    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);
+    }
+
+    // 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);
+}
+
+static inline bool isChildHitTestCandidate(RenderBox* box)
+{
+    return box->height() && box->style()->visibility() == VISIBLE && !box->isFloatingOrPositioned();
+}
+
+VisiblePosition RenderBlock::positionForPoint(const LayoutPoint& point)
+{
+    if (isTable())
+        return RenderBox::positionForPoint(point);
+
+    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 (pointLogicalTop < 0 || (pointLogicalTop < logicalHeight() && pointLogicalLeft < 0))
+            return createVisiblePosition(caretMinOffset(), DOWNSTREAM);
+        if (pointLogicalTop >= logicalHeight() || (pointLogicalTop >= 0 && pointLogicalLeft >= logicalWidth()))
+            return createVisiblePosition(caretMaxOffset(), DOWNSTREAM);
+    } 
+
+    LayoutPoint pointInContents = point;
+    offsetForContents(pointInContents);
+    LayoutPoint pointInLogicalContents(pointInContents);
+    if (!isHorizontalWritingMode())
+        pointInLogicalContents = pointInLogicalContents.transposedPoint();
+
+    if (childrenInline())
+        return positionForPointWithInlineChildren(pointInLogicalContents);
+
+    RenderBox* lastCandidateBox = lastChildBox();
+    while (lastCandidateBox && !isChildHitTestCandidate(lastCandidateBox))
+        lastCandidateBox = lastCandidateBox->previousSiblingBox();
+
+    if (lastCandidateBox) {
+        if (pointInContents.y() > lastCandidateBox->logicalTop())
+            return positionForPointRespectingEditingBoundaries(this, lastCandidateBox, pointInContents);
+
+        for (RenderBox* childBox = firstChildBox(); childBox; childBox = childBox->nextSiblingBox()) {
+            // We hit child if our click is above the bottom of its padding box (like IE6/7 and FF3).
+            if (isChildHitTestCandidate(childBox) && pointInContents.y() < childBox->logicalBottom())
+                return positionForPointRespectingEditingBoundaries(this, childBox, pointInContents);
+        }
+    }
+
+    // We only get here if there are no hit test candidate children below the click.
+    return RenderBox::positionForPoint(point);
+}
+
+void RenderBlock::offsetForContents(LayoutPoint& offset) const
+{
+    if (hasOverflowClip())
+        offset += layer()->scrolledContentOffset();
+
+    if (hasColumns())
+        adjustPointToColumnContents(offset);
+}
+
+LayoutUnit RenderBlock::availableLogicalWidth() const
+{
+    // If we have multiple columns, then the available logical width is reduced to our column width.
+    if (hasColumns())
+        return desiredColumnWidth();
+    return RenderBox::availableLogicalWidth();
+}
+
+int RenderBlock::columnGap() const
+{
+    if (style()->hasNormalColumnGap())
+        return style()->fontDescription().computedPixelSize(); // "1em" is recommended as the normal gap setting. Matches <p> margins.
+    return static_cast<int>(style()->columnGap());
+}
+
+void RenderBlock::calcColumnWidth()
+{    
+    // 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;
+    }
+    setDesiredColumnCountAndWidth(desiredColumnCount, desiredColumnWidth);
+}
+
+bool RenderBlock::requiresColumns(int desiredColumnCount) const
+{
+    return firstChild()
+        && (desiredColumnCount != 1 || !style()->hasAutoColumnWidth() || !style()->hasInlineColumnAxis())
+        && !firstChild()->isAnonymousColumnsBlock()
+        && !firstChild()->isAnonymousColumnSpanBlock();
+}
+
+void RenderBlock::setDesiredColumnCountAndWidth(int count, LayoutUnit width)
+{
+    bool destroyColumns = !requiresColumns(count);
+    if (destroyColumns) {
+        if (hasColumns()) {
+            delete gColumnInfoMap->take(this);
+            setHasColumns(false);
+        }
+    } else {
+        ColumnInfo* info;
+        if (hasColumns())
+            info = gColumnInfoMap->get(this);
+        else {
+            if (!gColumnInfoMap)
+                gColumnInfoMap = new ColumnInfoMap;
+            info = new ColumnInfo;
+            gColumnInfoMap->add(this, info);
+            setHasColumns(true);
+        }
+        info->setDesiredColumnCount(count);
+        info->setDesiredColumnWidth(width);
+        info->setProgressionAxis(style()->hasInlineColumnAxis() ? ColumnInfo::InlineAxis : ColumnInfo::BlockAxis);
+    }
+}
+
+LayoutUnit RenderBlock::desiredColumnWidth() const
+{
+    if (!hasColumns())
+        return contentLogicalWidth();
+    return gColumnInfoMap->get(this)->desiredColumnWidth();
+}
+
+unsigned RenderBlock::desiredColumnCount() const
+{
+    if (!hasColumns())
+        return 1;
+    return gColumnInfoMap->get(this)->desiredColumnCount();
+}
+
+ColumnInfo* RenderBlock::columnInfo() const
+{
+    if (!hasColumns())
+        return 0;
+    return gColumnInfoMap->get(this);    
+}
+
+unsigned RenderBlock::columnCount(ColumnInfo* colInfo) const
+{
+    ASSERT(hasColumns());
+    ASSERT(gColumnInfoMap->get(this) == colInfo);
+    return colInfo->columnCount();
+}
+
+LayoutRect RenderBlock::columnRectAt(ColumnInfo* colInfo, unsigned index) const
+{
+    ASSERT(hasColumns() && gColumnInfoMap->get(this) == colInfo);
+
+    // Compute the appropriate rect based off our information.
+    LayoutUnit colLogicalWidth = colInfo->desiredColumnWidth();
+    LayoutUnit colLogicalHeight = colInfo->columnHeight();
+    LayoutUnit colLogicalTop = borderBefore() + paddingBefore();
+    LayoutUnit colLogicalLeft = logicalLeftOffsetForContent();
+    int colGap = columnGap();
+    if (colInfo->progressionAxis() == ColumnInfo::InlineAxis) {
+        if (style()->isLeftToRightDirection())
+            colLogicalLeft += index * (colLogicalWidth + colGap);
+        else
+            colLogicalLeft += contentLogicalWidth() - colLogicalWidth - index * (colLogicalWidth + colGap);
+    } else
+        colLogicalTop += index * (colLogicalHeight + colGap);
+
+    if (isHorizontalWritingMode())
+        return LayoutRect(colLogicalLeft, colLogicalTop, colLogicalWidth, colLogicalHeight);
+    return LayoutRect(colLogicalTop, colLogicalLeft, colLogicalHeight, colLogicalWidth);
+}
+
+bool RenderBlock::layoutColumns(bool hasSpecifiedPageLogicalHeight, LayoutUnit pageLogicalHeight, LayoutStateMaintainer& statePusher)
+{
+    if (!hasColumns())
+        return false;
+
+    // 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(borderBefore() + paddingBefore() + contentLogicalHeight()) - colInfo->forcedBreakOffset());
+                columnHeight = max(colInfo->minimumColumnHeight(), distanceBetweenBreaks);
+            }
+        } else if (contentLogicalHeight() > pageLogicalHeight * desiredColumnCount) {
+            // Now that we know the intrinsic height of the columns, we have to rebalance them.
+            columnHeight = max<LayoutUnit>(colInfo->minimumColumnHeight(), ceilf((float)contentLogicalHeight() / desiredColumnCount));
+        }
+        
+        if (columnHeight && columnHeight != pageLogicalHeight) {
+            statePusher.pop();
+            setEverHadLayout(true);
+            layoutBlock(false, columnHeight);
+            return true;
+        }
+    } 
+    
+    if (pageLogicalHeight)
+        colInfo->setColumnCountAndHeight(ceilf((float)contentLogicalHeight() / pageLogicalHeight), pageLogicalHeight);
+
+    if (columnCount(colInfo)) {
+        setLogicalHeight(borderBefore() + paddingBefore() + colInfo->columnHeight() + borderAfter() + paddingAfter() + scrollbarLogicalHeight());
+        m_overflow.clear();
+    }
+    
+    return false;
+}
+
+void RenderBlock::adjustPointToColumnContents(LayoutPoint& point) const
+{
+    // Just bail if we have no columns.
+    if (!hasColumns())
+        return;
+    
+    ColumnInfo* colInfo = columnInfo();
+    if (!columnCount(colInfo))
+        return;
+
+    // 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()) {
+                // 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());
+                }
+
+                // 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(), logicalOffset);
+                else
+                    point.move((!style()->isFlippedBlocksWritingMode() ? logicalOffset : -logicalOffset) - colRect.x() + borderLeft() + paddingLeft(), 0);
+                return;
+            }
+            
+            // 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()) {
+                // 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);
+                }
+
+                // We're inside the column.  Translate the x and y into our column coordinate space.
+                if (colInfo->progressionAxis() == ColumnInfo::InlineAxis)
+                    point.move(logicalOffset, columnPoint.y() - colRect.y());
+                else
+                    point.move(0, (!style()->isFlippedBlocksWritingMode() ? logicalOffset : -logicalOffset) - colRect.y() + borderTop() + paddingTop());
+                return;
+            }
+            
+            // Move to the next position.
+            logicalOffset += colInfo->progressionAxis() == ColumnInfo::InlineAxis ? colRect.width() : colRect.height();
+        }
+    }
+}
+
+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;
+
+    // Begin with a result rect that is empty.
+    LayoutRect result;
+
+    bool isHorizontal = isHorizontalWritingMode();
+    LayoutUnit beforeBorderPadding = borderBefore() + paddingBefore();
+    LayoutUnit colHeight = colInfo->columnHeight();
+    if (!colHeight)
+        return;
+
+    LayoutUnit startOffset = max(isHorizontal ? r.y() : r.x(), beforeBorderPadding);
+    LayoutUnit endOffset = min<LayoutUnit>(isHorizontal ? r.maxY() : r.maxX(), beforeBorderPadding + colCount * colHeight);
+
+    // 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;
+
+    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;
+
+        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);
+        }
+        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 = borderBefore() + paddingBefore() + columnCount(colInfo) * columnLogicalHeight + borderAfter() + paddingAfter() + 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 = borderBefore() + paddingBefore() + columnCount(colInfo) * columnLogicalHeight + borderAfter() + paddingAfter() + scrollbarLogicalHeight();
+    
+    if (isHorizontalWritingMode())
+        rect.setY(expandedLogicalHeight - rect.maxY());
+    else
+        rect.setX(expandedLogicalHeight - rect.maxX());
+}
+
+void RenderBlock::adjustForColumns(LayoutSize& offset, const LayoutPoint& point) const
+{
+    if (!hasColumns())
+        return;
+
+    ColumnInfo* colInfo = columnInfo();
+
+    LayoutUnit logicalLeft = logicalLeftOffsetForContent();
+    size_t colCount = columnCount(colInfo);
+    LayoutUnit colLogicalWidth = colInfo->desiredColumnWidth();
+    LayoutUnit colLogicalHeight = colInfo->columnHeight();
+
+    for (size_t i = 0; i < colCount; ++i) {
+        // Compute the edges for a given column in the block progression direction.
+        LayoutRect sliceRect = LayoutRect(logicalLeft, borderBefore() + paddingBefore() + 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 - borderBefore() - paddingBefore());
+                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 - borderBefore() - paddingBefore(), 0);
+                return;
+            }
+        }
+    }
+}
+
+void RenderBlock::computePreferredLogicalWidths()
+{
+    ASSERT(preferredLogicalWidthsDirty());
+
+    updateFirstLetter();
+
+    if (!isTableCell() && style()->logicalWidth().isFixed() && style()->logicalWidth().value() > 0)
+        m_minPreferredLogicalWidth = m_maxPreferredLogicalWidth = computeContentBoxLogicalWidth(style()->logicalWidth().value());
+    else {
+        m_minPreferredLogicalWidth = 0;
+        m_maxPreferredLogicalWidth = 0;
+
+        if (childrenInline())
+            computeInlinePreferredLogicalWidths();
+        else
+            computeBlockPreferredLogicalWidths();
+
+        m_maxPreferredLogicalWidth = max(m_minPreferredLogicalWidth, m_maxPreferredLogicalWidth);
+
+        if (!style()->autoWrap() && childrenInline()) {
+            m_minPreferredLogicalWidth = m_maxPreferredLogicalWidth;
+            
+            // A horizontal marquee with inline children has no minimum width.
+            if (layer() && layer()->marquee() && layer()->marquee()->isHorizontal())
+                m_minPreferredLogicalWidth = 0;
+        }
+
+        int scrollbarWidth = 0;
+        if (hasOverflowClip() && style()->overflowY() == OSCROLL) {
+            layer()->setHasVerticalScrollbar(true);
+            scrollbarWidth = verticalScrollbarWidth();
+            m_maxPreferredLogicalWidth += scrollbarWidth;
+        }
+
+        if (isTableCell()) {
+            Length w = toRenderTableCell(this)->styleOrColLogicalWidth();
+            if (w.isFixed() && w.value() > 0) {
+                m_maxPreferredLogicalWidth = max(m_minPreferredLogicalWidth, computeContentBoxLogicalWidth(w.value()));
+                scrollbarWidth = 0;
+            }
+        }
+        
+        m_minPreferredLogicalWidth += scrollbarWidth;
+    }
+    
+    if (style()->logicalMinWidth().isFixed() && style()->logicalMinWidth().value() > 0) {
+        m_maxPreferredLogicalWidth = max(m_maxPreferredLogicalWidth, computeContentBoxLogicalWidth(style()->logicalMinWidth().value()));
+        m_minPreferredLogicalWidth = max(m_minPreferredLogicalWidth, computeContentBoxLogicalWidth(style()->logicalMinWidth().value()));
+    }
+    
+    if (style()->logicalMaxWidth().isFixed()) {
+        m_maxPreferredLogicalWidth = min(m_maxPreferredLogicalWidth, computeContentBoxLogicalWidth(style()->logicalMaxWidth().value()));
+        m_minPreferredLogicalWidth = min(m_minPreferredLogicalWidth, computeContentBoxLogicalWidth(style()->logicalMaxWidth().value()));
+    }
+
+    LayoutUnit borderAndPadding = borderAndPaddingLogicalWidth();
+    m_minPreferredLogicalWidth += borderAndPadding;
+    m_maxPreferredLogicalWidth += borderAndPadding;
+
+    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->isPositioned())))
+            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->isPositioned() && (result->isText() || result->isFloating() || result->isReplaced() || result->isRenderInline()))
+             break;
+        
+        current = result;
+        result = 0;
+    }
+
+    // Update our position.
+    current = result;
+    return current;
+}
+
+static int getBPMWidth(int childValue, Length cssUnit)
+{
+    if (cssUnit.type() != Auto)
+        return (cssUnit.isFixed() ? cssUnit.value() : childValue);
+    return 0;
+}
+
+static int getBorderPaddingMargin(const RenderBoxModelObject* child, bool endOfInline)
+{
+    RenderStyle* cstyle = child->style();
+    if (endOfInline)
+        return getBPMWidth(child->marginEnd(), cstyle->marginEnd()) + 
+               getBPMWidth(child->paddingEnd(), cstyle->paddingEnd()) +
+               child->borderEnd();
+    return getBPMWidth(child->marginStart(), cstyle->marginStart()) + 
+               getBPMWidth(child->paddingStart(), cstyle->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);
+}
+
+void RenderBlock::computeInlinePreferredLogicalWidths()
+{
+    float inlineMax = 0;
+    float inlineMin = 0;
+
+    RenderBlock* containingBlock = this->containingBlock();
+    LayoutUnit cw = containingBlock ? containingBlock->contentLogicalWidth() : 0;
+
+    // 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() || !style()->logicalWidth().isIntrinsicOrAuto();
+
+    bool autoWrap, oldAutoWrap;
+    autoWrap = oldAutoWrap = style()->autoWrap();
+
+    InlineMinMaxIterator childIterator(this);
+    bool addedTextIndent = false; // Only gets added in once.
+    RenderObject* prevFloat = 0;
+    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* cstyle = 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.
+                    float margins = 0;
+                    Length startMargin = cstyle->marginStart();
+                    Length endMargin = cstyle->marginEnd();
+                    if (startMargin.isFixed())
+                        margins += startMargin.value();
+                    if (endMargin.isFixed())
+                        margins += endMargin.value();
+                    childMin += margins;
+                    childMax += margins;
+                }
+            }
+
+            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();
+                childMax += child->maxPreferredLogicalWidth();
+
+                bool clearPreviousFloat;
+                if (child->isFloating()) {
+                    clearPreviousFloat = (prevFloat
+                        && ((prevFloat->style()->floating() == LeftFloat && (child->style()->clear() & CLEFT))
+                            || (prevFloat->style()->floating() == RightFloat && (child->style()->clear() & CRIGHT))));
+                    prevFloat = child;
+                } else
+                    clearPreviousFloat = false;
+
+                bool canBreakReplacedElement = !child->isImage() || allowImagesToBreak;
+                if ((canBreakReplacedElement && (autoWrap || oldAutoWrap)) || clearPreviousFloat) {
+                    updatePreferredWidth(m_minPreferredLogicalWidth, inlineMin);
+                    inlineMin = 0;
+                }
+
+                // If we're supposed to clear the previous float, then terminate maxwidth as well.
+                if (clearPreviousFloat) {
+                    updatePreferredWidth(m_maxPreferredLogicalWidth, inlineMax);
+                    inlineMax = 0;
+                }
+
+                // Add in text-indent.  This is added in only once.
+                LayoutUnit ti = 0;
+                if (!addedTextIndent) {
+                    addedTextIndent = true;
+                    ti = style()->textIndent().calcMinValue(cw);
+                    childMin += ti;
+                    childMax += ti;
+                }
+
+                // Add our width to the max.
+                inlineMax += childMax;
+
+                if (!autoWrap || !canBreakReplacedElement) {
+                    if (child->isFloating())
+                        updatePreferredWidth(m_minPreferredLogicalWidth, childMin);
+                    else
+                        inlineMin += childMin;
+                } else {
+                    // Now check our line.
+                    updatePreferredWidth(m_minPreferredLogicalWidth, childMin);
+
+                    // Now start a new line.
+                    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(m_minPreferredLogicalWidth, 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(m_minPreferredLogicalWidth, inlineMin);
+                        inlineMin = 0;
+                    }
+                    continue;
+                }
+                
+                if (stripFrontSpaces)
+                    trailingSpaceChild = child;
+                else
+                    trailingSpaceChild = 0;
+
+                // Add in text-indent.  This is added in only once.
+                LayoutUnit ti = 0;
+                if (!addedTextIndent) {
+                    addedTextIndent = true;
+                    ti = style()->textIndent().calcMinValue(cw);
+                    childMin+=ti; beginMin += ti;
+                    childMax+=ti; beginMax += ti;
+                }
+                
+                // 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(m_minPreferredLogicalWidth, inlineMin);
+                    else {
+                        inlineMin += beginMin;
+                        updatePreferredWidth(m_minPreferredLogicalWidth, inlineMin);
+                        childMin -= ti;
+                    }
+
+                    inlineMin = childMin;
+
+                    if (endWS) {
+                        // We end in whitespace, which means we can go ahead
+                        // and end our current line.
+                        updatePreferredWidth(m_minPreferredLogicalWidth, inlineMin);
+                        inlineMin = 0;
+                    } else {
+                        updatePreferredWidth(m_minPreferredLogicalWidth, inlineMin);
+                        inlineMin = endMin;
+                    }
+                }
+
+                if (hasBreak) {
+                    inlineMax += beginMax;
+                    updatePreferredWidth(m_maxPreferredLogicalWidth, inlineMax);
+                    updatePreferredWidth(m_maxPreferredLogicalWidth, childMax);
+                    inlineMax = endMax;
+                } else
+                    inlineMax += childMax;
+            }
+
+            // Ignore spaces after a list marker.
+            if (child->isListMarker())
+                stripFrontSpaces = true;
+        } else {
+            updatePreferredWidth(m_minPreferredLogicalWidth, inlineMin);
+            updatePreferredWidth(m_maxPreferredLogicalWidth, inlineMax);
+            inlineMin = inlineMax = 0;
+            stripFrontSpaces = true;
+            trailingSpaceChild = 0;
+        }
+
+        oldAutoWrap = autoWrap;
+    }
+
+    if (style()->collapseWhiteSpace())
+        stripTrailingSpace(inlineMax, inlineMin, trailingSpaceChild);
+
+    updatePreferredWidth(m_minPreferredLogicalWidth, inlineMin);
+    updatePreferredWidth(m_maxPreferredLogicalWidth, inlineMax);
+}
+
+// Use a very large value (in effect infinite).
+#define BLOCK_MAX_WIDTH 15000
+
+void RenderBlock::computeBlockPreferredLogicalWidths()
+{
+    bool nowrap = style()->whiteSpace() == NOWRAP;
+
+    RenderObject* child = firstChild();
+    RenderBlock* containingBlock = this->containingBlock();
+    LayoutUnit floatLeftWidth = 0, floatRightWidth = 0;
+    while (child) {
+        // Positioned children don't affect the min/max width
+        if (child->isPositioned()) {
+            child = child->nextSibling();
+            continue;
+        }
+
+        if (child->isFloating() || (child->isBox() && toRenderBox(child)->avoidsFloats())) {
+            LayoutUnit floatTotalWidth = floatLeftWidth + floatRightWidth;
+            if (child->style()->clear() & CLEFT) {
+                m_maxPreferredLogicalWidth = max(floatTotalWidth, m_maxPreferredLogicalWidth);
+                floatLeftWidth = 0;
+            }
+            if (child->style()->clear() & CRIGHT) {
+                m_maxPreferredLogicalWidth = max(floatTotalWidth, m_maxPreferredLogicalWidth);
+                floatRightWidth = 0;
+            }
+        }
+
+        // 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 = child->style()->marginStartUsing(style());
+        Length endMarginLength = child->style()->marginEndUsing(style());
+        LayoutUnit margin = 0;
+        LayoutUnit marginStart = 0;
+        LayoutUnit marginEnd = 0;
+        if (startMarginLength.isFixed())
+            marginStart += startMarginLength.value();
+        if (endMarginLength.isFixed())
+            marginEnd += endMarginLength.value();
+        margin = marginStart + marginEnd;
+
+        LayoutUnit childMinPreferredLogicalWidth, childMaxPreferredLogicalWidth;
+        if (child->isBox() && child->isHorizontalWritingMode() != isHorizontalWritingMode()) {
+            RenderBox* childBox = toRenderBox(child);
+            LayoutUnit oldHeight = childBox->logicalHeight();
+            childBox->setLogicalHeight(childBox->borderAndPaddingLogicalHeight());
+            childBox->computeLogicalHeight();
+            childMinPreferredLogicalWidth = childMaxPreferredLogicalWidth = childBox->logicalHeight();
+            childBox->setLogicalHeight(oldHeight);
+        } else {
+            childMinPreferredLogicalWidth = child->minPreferredLogicalWidth();
+            childMaxPreferredLogicalWidth = child->maxPreferredLogicalWidth();
+        }
+
+        LayoutUnit w = childMinPreferredLogicalWidth + margin;
+        m_minPreferredLogicalWidth = max(w, m_minPreferredLogicalWidth);
+        
+        // IE ignores tables for calculation of nowrap. Makes some sense.
+        if (nowrap && !child->isTable())
+            m_maxPreferredLogicalWidth = max(w, m_maxPreferredLogicalWidth);
+
+        w = childMaxPreferredLogicalWidth + margin;
+
+        if (!child->isFloating()) {
+            if (child->isBox() && toRenderBox(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() : style()->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;
+                w = childMaxPreferredLogicalWidth + maxLeft + maxRight;
+                w = max(w, floatLeftWidth + floatRightWidth);
+            }
+            else
+                m_maxPreferredLogicalWidth = max(floatLeftWidth + floatRightWidth, m_maxPreferredLogicalWidth);
+            floatLeftWidth = floatRightWidth = 0;
+        }
+        
+        if (child->isFloating()) {
+            if (style()->floating() == LeftFloat)
+                floatLeftWidth += w;
+            else
+                floatRightWidth += w;
+        } else
+            m_maxPreferredLogicalWidth = max(w, m_maxPreferredLogicalWidth);
+        
+        child = child->nextSibling();
+    }
+
+    // Always make sure these values are non-negative.
+    m_minPreferredLogicalWidth = max<LayoutUnit>(0, m_minPreferredLogicalWidth);
+    m_maxPreferredLogicalWidth = max<LayoutUnit>(0, m_maxPreferredLogicalWidth);
+
+    m_maxPreferredLogicalWidth = max(floatLeftWidth + floatRightWidth, m_maxPreferredLogicalWidth);
+}
+
+bool RenderBlock::hasLineIfEmpty() const
+{
+    if (!node())
+        return false;
+    
+    if (node()->rendererIsEditable() && node()->rootEditableElement() == node())
+        return true;
+    
+    if (node()->isShadowRoot() && (node()->shadowHost()->hasTagName(inputTag)))
+        return true;
+    
+    return false;
+}
+
+LayoutUnit RenderBlock::lineHeight(bool firstLine, LineDirectionMode direction, LinePositionMode linePositionMode) const
+{
+    // 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
+    // just like a block.
+    if (isReplaced() && linePositionMode == PositionOnContainingLine)
+        return RenderBox::lineHeight(firstLine, direction, linePositionMode);
+
+    if (firstLine && document()->usesFirstLineRules()) {
+        RenderStyle* s = style(firstLine);
+        if (s != style())
+            return s->computedLineHeight();
+    }
+    
+    if (m_lineHeight == -1)
+        m_lineHeight = style()->computedLineHeight();
+
+    return m_lineHeight;
+}
+
+LayoutUnit RenderBlock::baselinePosition(FontBaseline baselineType, bool firstLine, LineDirectionMode direction, LinePositionMode linePositionMode) const
+{
+    // 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
+    // just like a block.
+    if (isReplaced() && linePositionMode == PositionOnContainingLine) {
+        // 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);
+            
+        // 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 ? LayoutUnit(-1) : lastLineBoxBaseline();
+        
+        int 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;
+}
+
+LayoutUnit 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->isFloatingOrPositioned()) {
+                LayoutUnit result = curr->firstLineBoxBaseline();
+                if (result != -1)
+                    return curr->logicalTop() + result; // Translate to our coordinate space.
+            }
+        }
+    }
+
+    return -1;
+}
+
+LayoutUnit RenderBlock::lastLineBoxBaseline() const
+{
+    if (!isBlockFlow() || (isWritingModeRoot() && !isRubyRun()))
+        return -1;
+
+    LineDirectionMode lineDirection = isHorizontalWritingMode() ? HorizontalLine : VerticalLine;
+
+    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->isFloatingOrPositioned()) {
+                haveNormalFlowChild = true;
+                LayoutUnit result = curr->lastLineBoxBaseline();
+                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();
+        if (firstLineBlock->isReplaced() || firstLineBlock->isFloating() || 
+            !parentBlock || parentBlock->firstChild() != firstLineBlock || !parentBlock->isBlockFlow())
+            break;
+        ASSERT(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);
+}
+
+void RenderBlock::updateFirstLetter()
+{
+    if (!document()->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 = this;
+    bool hasPseudoStyle = false;
+    while (true) {
+        // We only honor first-letter if the firstLetterBlock can have children in the DOM. This correctly 
+        // prevents form controls from honoring first-letter.
+        hasPseudoStyle = firstLetterBlock->style()->hasPseudoStyle(FIRST_LETTER) 
+            && firstLetterBlock->canHaveChildren();
+        if (hasPseudoStyle)
+            break;
+        RenderObject* parentBlock = firstLetterBlock->parent();
+        if (firstLetterBlock->isReplaced() || !parentBlock || parentBlock->firstChild() != firstLetterBlock || 
+            !parentBlock->isBlockFlow())
+            break;
+        firstLetterBlock = parentBlock;
+    } 
+
+    if (!hasPseudoStyle) 
+        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->isFloatingOrPositioned()) {
+            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->canHaveChildren())  {
+            // 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) {
+        RenderObject* firstLetter = currChild->parent();
+        RenderObject* firstLetterContainer = firstLetter->parent();
+        RenderStyle* pseudoStyle = styleForFirstLetter(firstLetterBlock, firstLetterContainer);
+        ASSERT(firstLetter->isFloating() || firstLetter->isInline());
+
+        if (Node::diff(firstLetter->style(), pseudoStyle) == 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 = new (renderArena()) RenderInline(document());
+            else
+                newFirstLetter = new (renderArena()) RenderBlock(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);
+            }
+            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);
+        }
+
+        return;
+    }
+
+    if (!currChild->isText() || currChild->isBR())
+        return;
+
+    // If the child does not already have style, we create it here.
+    RenderObject* firstLetterContainer = currChild->parent();
+
+    // Our layout state is not valid for the repaints we are going to trigger by
+    // adding and removing children of firstLetterContainer.
+    LayoutStateDisabler layoutStateDisabler(view());
+
+    RenderText* textObj = toRenderText(currChild);
+
+    // Create our pseudo style now that we have our firstLetterContainer determined.
+    RenderStyle* pseudoStyle = styleForFirstLetter(firstLetterBlock, firstLetterContainer);
+
+    RenderObject* firstLetter = 0;
+    if (pseudoStyle->display() == INLINE)
+        firstLetter = new (renderArena()) RenderInline(document());
+    else
+        firstLetter = new (renderArena()) RenderBlock(document());
+    firstLetter->setStyle(pseudoStyle);
+    firstLetterContainer->addChild(firstLetter, currChild);
+
+    // 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);
+        
+        // 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();
+    }
+}
+
+// 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->isFloatingOrPositioned() && !obj->isRunIn() &&
+            obj->isBlockFlow() && obj->style()->height().isAuto() &&
+            (!obj->isDeprecatedFlexibleBox() || obj->style()->boxOrient() == VERTICAL);
+}
+
+static RootInlineBox* getLineAtIndex(RenderBlock* block, int i, int& count)
+{
+    if (block->style()->visibility() == VISIBLE) {
+        if (block->childrenInline()) {
+            for (RootInlineBox* box = block->firstRootBox(); box; box = box->nextRootBox()) {
+                if (count++ == i)
+                    return box;
+            }
+        }
+        else {
+            for (RenderObject* obj = block->firstChild(); obj; obj = obj->nextSibling()) {
+                if (shouldCheckLines(obj)) {
+                    RootInlineBox *box = getLineAtIndex(toRenderBlock(obj), i, count);
+                    if (box)
+                        return box;
+                }
+            }
+        }
+    }
+    return 0;
+}
+
+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()) : 0);
+            }
+        }
+        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()) : 0);
+                }
+                else if (!obj->isFloatingOrPositioned() && !obj->isRunIn())
+                    normalFlowChildWithoutLines = obj;
+            }
+            if (normalFlowChildWithoutLines && l == 0)
+                return normalFlowChildWithoutLines->y() + normalFlowChildWithoutLines->height();
+        }
+    }
+    
+    return -1;
+}
+
+RootInlineBox* RenderBlock::lineAtIndex(int i)
+{
+    int count = 0;
+    return getLineAtIndex(this, i, count);
+}
+
+int RenderBlock::lineCount()
+{
+    int count = 0;
+    if (style()->visibility() == VISIBLE) {
+        if (childrenInline())
+            for (RootInlineBox* box = firstRootBox(); box; box = box->nextRootBox())
+                count++;
+        else
+            for (RenderObject* obj = firstChild(); obj; obj = obj->nextSibling())
+                if (shouldCheckLines(obj))
+                    count += toRenderBlock(obj)->lineCount();
+    }
+    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->isFloatingOrPositioned()) {
+                    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());
+                    }
+                }
+            }
+        }
+        
+        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->m_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::borderFitAdjust(LayoutRect& rect) const
+{
+    if (style()->borderFit() == BorderFitBorder)
+        return;
+
+    // Walk any normal flow lines to snugly fit.
+    LayoutUnit left = numeric_limits<LayoutUnit>::max();
+    LayoutUnit right = numeric_limits<LayoutUnit>::min();
+    LayoutUnit oldWidth = rect.width();
+    adjustForBorderFit(0, left, right);
+    if (left != numeric_limits<LayoutUnit>::max()) {
+        left = min(left, oldWidth - (borderRight() + paddingRight()));
+
+        left -= (borderLeft() + paddingLeft());
+        if (left > 0) {
+            rect.move(left, 0);
+            rect.expand(-left, 0);
+        }
+    }
+    if (right != numeric_limits<LayoutUnit>::min()) {
+        right = max(right, borderLeft() + paddingLeft());
+
+        right += (borderRight() + paddingRight());
+        if (right < oldWidth)
+            rect.expand(-(oldWidth - right), 0);
+    }
+}
+
+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));
+    }
+    m_rareData->m_margins.setPositiveMarginBefore(pos);
+    m_rareData->m_margins.setNegativeMarginBefore(neg);
+}
+
+void RenderBlock::setMaxMarginAfterValues(LayoutUnit pos, LayoutUnit neg)
+{
+    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);
+}
+
+void RenderBlock::setPaginationStrut(LayoutUnit strut)
+{
+    if (!m_rareData) {
+        if (!strut)
+            return;
+        m_rareData = adoptPtr(new RenderBlockRareData(this));
+    }
+    m_rareData->m_paginationStrut = strut;
+}
+
+void RenderBlock::setPageLogicalOffset(int logicalOffset)
+{
+    if (!m_rareData) {
+        if (!logicalOffset)
+            return;
+        m_rareData = adoptPtr(new RenderBlockRareData(this));
+    }
+    m_rareData->m_pageLogicalOffset = logicalOffset;
+}
+
+void RenderBlock::absoluteRects(Vector<LayoutRect>& 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(LayoutRect(accumulatedOffset.x(), accumulatedOffset.y() - collapsedMarginBefore(),
+                                width(), height() + collapsedMarginBefore() + collapsedMarginAfter()));
+        continuation()->absoluteRects(rects, accumulatedOffset - toLayoutSize(location() +
+                inlineElementContinuation()->containingBlock()->location()));
+    } else
+        rects.append(LayoutRect(accumulatedOffset, size()));
+}
+
+void RenderBlock::absoluteQuads(Vector<FloatQuad>& quads, bool* wasFixed) 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
+        FloatRect localRect(0, -collapsedMarginBefore(),
+                            width(), height() + collapsedMarginBefore() + collapsedMarginAfter());
+        quads.append(localToAbsoluteQuad(localRect, false, wasFixed));
+        continuation()->absoluteQuads(quads, wasFixed);
+    } else
+        quads.append(RenderBox::localToAbsoluteQuad(FloatRect(0, 0, width(), height()), false, wasFixed));
+}
+
+LayoutRect RenderBlock::rectWithOutlineForRepaint(RenderBoxModelObject* 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;
+}
+
+RenderObject* RenderBlock::hoverAncestor() const
+{
+    return isAnonymousBlockContinuation() ? continuation() : RenderBox::hoverAncestor();
+}
+
+void RenderBlock::updateDragState(bool dragOn)
+{
+    RenderBox::updateDragState(dragOn);
+    if (continuation())
+        continuation()->updateDragState(dragOn);
+}
+
+RenderStyle* RenderBlock::outlineStyleForRepaint() const
+{
+    return isAnonymousBlockContinuation() ? continuation()->style() : style();
+}
+
+void RenderBlock::childBecameNonInline(RenderObject*)
+{
+    makeChildrenNonInline();
+    if (isAnonymousBlock() && parent() && parent()->isRenderBlock())
+        toRenderBlock(parent())->removeLeftoverAnonymousBlock(this);
+    // |this| may be dead here
+}
+
+void RenderBlock::updateHitTestResult(HitTestResult& result, const LayoutPoint& point)
+{
+    if (result.innerNode())
+        return;
+
+    Node* n = node();
+    if (isAnonymousBlockContinuation())
+        // We are in the margins of block elements that are part of a continuation.  In
+        // this case we're actually still inside the enclosing element that was
+        // split.  Go ahead and set our inner node accordingly.
+        n = continuation()->node();
+
+    if (n) {
+        result.setInnerNode(n);
+        if (!result.innerNonSharedNode())
+            result.setInnerNonSharedNode(n);
+        result.setLocalPoint(point);
+    }
+}
+
+LayoutRect RenderBlock::localCaretRect(InlineBox* inlineBox, int caretOffset, LayoutUnit* extraWidthToEndOfLine)
+{
+    // Do the normal calculation in most cases.
+    if (firstChild())
+        return RenderBox::localCaretRect(inlineBox, caretOffset, extraWidthToEndOfLine);
+
+    // This is a special case:
+    // The element is not an inline element, and it's empty. So we have to
+    // calculate a fake position to indicate where objects are to be inserted.
+    
+    // FIXME: This does not take into account either :first-line or :first-letter
+    // However, as soon as some content is entered, the line boxes will be
+    // constructed and this kludge is not called any more. So only the caret size
+    // of an empty :first-line'd block is wrong. I think we can live with that.
+    RenderStyle* currentStyle = firstLineStyle();
+    LayoutUnit height = lineHeight(true, currentStyle->isHorizontalWritingMode() ? HorizontalLine : VerticalLine);
+
+    enum CaretAlignment { alignLeft, alignRight, alignCenter };
+
+    CaretAlignment alignment = alignLeft;
+
+    switch (currentStyle->textAlign()) {
+        case TAAUTO:
+        case JUSTIFY:
+            if (!currentStyle->isLeftToRightDirection())
+                alignment = alignRight;
+            break;
+        case LEFT:
+        case WEBKIT_LEFT:
+            break;
+        case CENTER:
+        case WEBKIT_CENTER:
+            alignment = alignCenter;
+            break;
+        case RIGHT:
+        case WEBKIT_RIGHT:
+            alignment = alignRight;
+            break;
+        case TASTART:
+            if (!currentStyle->isLeftToRightDirection())
+                alignment = alignRight;
+            break;
+        case TAEND:
+            if (currentStyle->isLeftToRightDirection())
+                alignment = alignRight;
+            break;
+    }
+
+    LayoutUnit x = borderLeft() + paddingLeft();
+    LayoutUnit w = width();
+
+    switch (alignment) {
+        case alignLeft:
+            break;
+        case alignCenter:
+            x = (x + w - (borderRight() + paddingRight())) / 2;
+            break;
+        case alignRight:
+            x = w - (borderRight() + paddingRight()) - caretWidth;
+            break;
+    }
+
+    if (extraWidthToEndOfLine) {
+        if (isRenderBlock()) {
+            *extraWidthToEndOfLine = w - (x + caretWidth);
+        } else {
+            // FIXME: This code looks wrong.
+            // myRight and containerRight are set up, but then clobbered.
+            // So *extraWidthToEndOfLine will always be 0 here.
+
+            LayoutUnit myRight = x + caretWidth;
+            // FIXME: why call localToAbsoluteForContent() twice here, too?
+            FloatPoint absRightPoint = localToAbsolute(FloatPoint(myRight, 0));
+
+            LayoutUnit containerRight = containingBlock()->x() + containingBlockLogicalWidthForContent();
+            FloatPoint absContainerPoint = localToAbsolute(FloatPoint(containerRight, 0));
+
+            *extraWidthToEndOfLine = absContainerPoint.x() - absRightPoint.x();
+        }
+    }
+
+    LayoutUnit y = paddingTop() + borderTop();
+
+    return LayoutRect(x, y, caretWidth, height);
+}
+
+void RenderBlock::addFocusRingRects(Vector<LayoutRect>& rects, const LayoutPoint& additionalOffset)
+{
+    // 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() : static_cast<LayoutUnit>(0);
+        float bottomMargin = nextInlineHasLineBox ? collapsedMarginAfter() : static_cast<LayoutUnit>(0);
+        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()));
+
+    if (!hasOverflowClip() && !hasControlClip()) {
+        for (RootInlineBox* curr = firstRootBox(); curr; curr = curr->nextRootBox()) {
+            LayoutUnit top = max(curr->lineTop(), static_cast<LayoutUnit>(curr->top()));
+            LayoutUnit bottom = min(curr->lineBottom(), static_cast<LayoutUnit>(curr->top() + curr->height()));
+            LayoutRect rect(additionalOffset.x() + curr->x(), additionalOffset.y() + top, curr->width(), bottom - top);
+            if (!rect.isEmpty())
+                rects.append(rect);
+        }
+
+        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->localToAbsolute();
+                else
+                    pos = FloatPoint(additionalOffset.x() + box->x(), additionalOffset.y() + box->y());
+                box->addFocusRingRects(rects, flooredLayoutPoint(pos));
+            }
+        }
+    }
+
+    if (inlineElementContinuation())
+        inlineElementContinuation()->addFocusRingRects(rects, flooredLayoutPoint(additionalOffset + inlineElementContinuation()->containingBlock()->location() - location()));
+}
+
+RenderBlock* RenderBlock::createAnonymousBlock(bool isFlexibleBox) const
+{
+    RefPtr<RenderStyle> newStyle = RenderStyle::createAnonymousStyle(style());
+
+    RenderBlock* newBox = 0;
+    if (isFlexibleBox) {
+        newStyle->setDisplay(BOX);
+        newBox = new (renderArena()) RenderDeprecatedFlexibleBox(document() /* anonymous box */);
+    } else {
+        newStyle->setDisplay(BLOCK);
+        newBox = new (renderArena()) RenderBlock(document() /* anonymous box */);
+    }
+
+    newBox->setStyle(newStyle.release());
+    return newBox;
+}
+
+RenderBlock* RenderBlock::createAnonymousBlockWithSameTypeAs(RenderBlock* otherAnonymousBlock) const
+{
+    if (otherAnonymousBlock->isAnonymousColumnsBlock())
+        return createAnonymousColumnsBlock();
+    if (otherAnonymousBlock->isAnonymousColumnSpanBlock())
+        return createAnonymousColumnSpanBlock();
+    return createAnonymousBlock(otherAnonymousBlock->style()->display() == BOX);
+}
+
+RenderBlock* RenderBlock::createAnonymousColumnsBlock() const
+{
+    RefPtr<RenderStyle> newStyle = RenderStyle::createAnonymousStyle(style());
+    newStyle->inheritColumnPropertiesFrom(style());
+    newStyle->setDisplay(BLOCK);
+
+    RenderBlock* newBox = new (renderArena()) RenderBlock(document() /* anonymous box */);
+    newBox->setStyle(newStyle.release());
+    return newBox;
+}
+
+RenderBlock* RenderBlock::createAnonymousColumnSpanBlock() const
+{
+    RefPtr<RenderStyle> newStyle = RenderStyle::createAnonymousStyle(style());
+    newStyle->setColumnSpan(ColumnSpanAll);
+    newStyle->setDisplay(BLOCK);
+
+    RenderBlock* newBox = new (renderArena()) RenderBlock(document() /* anonymous box */);
+    newBox->setStyle(newStyle.release());
+    return newBox;
+}
+
+bool RenderBlock::hasNextPage(LayoutUnit logicalOffset, PageBoundaryRule pageBoundaryRule) const
+{
+    ASSERT(view()->layoutState() && view()->layoutState()->isPaginated());
+
+    if (!inRenderFlowThread())
+        return true; // Printing and multi-column both make new pages to accommodate content.
+
+    // See if we're in the last region.
+    LayoutUnit pageOffset = offsetFromLogicalTopOfFirstPage() + logicalOffset;
+    RenderRegion* region = enclosingRenderFlowThread()->renderRegionForLine(pageOffset, this);
+    if (!region)
+        return false;
+    if (region->isLastRegion())
+        return region->style()->regionOverflow() == BreakRegionOverflow
+            || (pageBoundaryRule == IncludePageBoundary && pageOffset == region->offsetFromLogicalTopOfFirstPage());
+    return true;
+}
+
+LayoutUnit RenderBlock::nextPageLogicalTop(LayoutUnit logicalOffset, PageBoundaryRule pageBoundaryRule) const
+{
+    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;
+}
+
+static bool inNormalFlow(RenderBox* child)
+{
+    RenderBlock* curr = child->containingBlock();
+    RenderView* renderView = child->view();
+    while (curr && curr != renderView) {
+        if (curr->hasColumns() || curr->isRenderFlowThread())
+            return true;
+        if (curr->isFloatingOrPositioned())
+            return false;
+        curr = curr->containingBlock();
+    }
+    return true;
+}
+
+LayoutUnit RenderBlock::applyBeforeBreak(RenderBox* child, LayoutUnit logicalOffset)
+{
+    // 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.
+    bool checkRegionBreaks = inRenderFlowThread();
+    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(logicalOffset);
+        return nextPageLogicalTop(logicalOffset, IncludePageBoundary);
+    }
+    return logicalOffset;
+}
+
+LayoutUnit RenderBlock::applyAfterBreak(RenderBox* child, LayoutUnit logicalOffset, MarginInfo& marginInfo)
+{
+    // 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.
+    bool checkRegionBreaks = inRenderFlowThread();
+    bool checkAfterAlways = (checkColumnBreaks && child->style()->columnBreakAfter() == PBALWAYS) || (checkPageBreaks && child->style()->pageBreakAfter() == PBALWAYS)
+                            || (checkRegionBreaks && child->style()->regionBreakAfter() == PBALWAYS);
+    if (checkAfterAlways && inNormalFlow(child) && hasNextPage(logicalOffset, IncludePageBoundary)) {
+        marginInfo.setMarginAfterQuirk(true); // Cause margins to be discarded for any following content.
+        if (checkColumnBreaks)
+            view()->layoutState()->addForcedColumnBreak(logicalOffset);
+        return nextPageLogicalTop(logicalOffset, IncludePageBoundary);
+    }
+    return logicalOffset;
+}
+
+LayoutUnit RenderBlock::pageLogicalHeightForOffset(LayoutUnit offset) const
+{
+    RenderView* renderView = view();
+    if (!inRenderFlowThread())
+        return renderView->layoutState()->m_pageLogicalHeight;
+    return enclosingRenderFlowThread()->regionLogicalHeightForLine(offset + offsetFromLogicalTopOfFirstPage());
+}
+
+LayoutUnit RenderBlock::pageRemainingLogicalHeightForOffset(LayoutUnit offset, PageBoundaryRule pageBoundaryRule) const
+{
+    RenderView* renderView = view();
+    offset += offsetFromLogicalTopOfFirstPage();
+    
+    if (!inRenderFlowThread()) {
+        LayoutUnit pageLogicalHeight = renderView->layoutState()->m_pageLogicalHeight;
+        LayoutUnit remainingHeight = pageLogicalHeight - layoutMod(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 = layoutMod(remainingHeight, pageLogicalHeight);
+        }
+        return remainingHeight;
+    }
+    
+    return enclosingRenderFlowThread()->regionRemainingLogicalHeightForLine(offset, pageBoundaryRule);
+}
+
+LayoutUnit RenderBlock::adjustForUnsplittableChild(RenderBox* child, LayoutUnit logicalOffset, bool includeMargins)
+{
+    bool isUnsplittable = child->isUnsplittableForPagination() || child->style()->columnBreakInside() == PBAVOID
+        || child->style()->regionBreakInside() == PBAVOID;
+    if (!isUnsplittable)
+        return logicalOffset;
+    LayoutUnit childLogicalHeight = logicalHeightForChild(child) + (includeMargins ? marginBeforeForChild(child) + marginAfterForChild(child) : 0);
+    LayoutState* layoutState = view()->layoutState();
+    if (layoutState->m_columnInfo)
+        layoutState->m_columnInfo->updateMinimumColumnHeight(childLogicalHeight);
+    LayoutUnit pageLogicalHeight = pageLogicalHeightForOffset(logicalOffset);
+    bool hasUniformPageLogicalHeight = !inRenderFlowThread() || enclosingRenderFlowThread()->regionsHaveUniformLogicalHeight();
+    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;
+}
+
+bool RenderBlock::pushToNextPageWithMinimumLogicalHeight(LayoutUnit& adjustment, LayoutUnit logicalOffset, LayoutUnit minimumLogicalHeight) 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;
+}
+
+void RenderBlock::adjustLinePositionForPagination(RootInlineBox* lineBox, LayoutUnit& delta)
+{
+    // 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 lineHeight = max(lineBox->lineBottomWithLeading(), logicalVisualOverflow.maxY()) - logicalOffset;
+    RenderView* renderView = view();
+    LayoutState* layoutState = renderView->layoutState();
+    if (layoutState->m_columnInfo)
+        layoutState->m_columnInfo->updateMinimumColumnHeight(lineHeight);
+    logicalOffset += delta;
+    lineBox->setPaginationStrut(0);
+    LayoutUnit pageLogicalHeight = pageLogicalHeightForOffset(logicalOffset);
+    bool hasUniformPageLogicalHeight = !inRenderFlowThread() || enclosingRenderFlowThread()->regionsHaveUniformLogicalHeight();
+    if (!pageLogicalHeight || (hasUniformPageLogicalHeight && lineHeight > pageLogicalHeight)
+        || !hasNextPage(logicalOffset))
+        return;
+    LayoutUnit remainingLogicalHeight = pageRemainingLogicalHeightForOffset(logicalOffset, ExcludePageBoundary);
+    if (remainingLogicalHeight < lineHeight) {
+        // If we have a non-uniform page height, then we have to shift further possibly.
+        if (!hasUniformPageLogicalHeight && !pushToNextPageWithMinimumLogicalHeight(remainingLogicalHeight, logicalOffset, lineHeight))
+            return;
+        LayoutUnit totalLogicalHeight = lineHeight + max<LayoutUnit>(0, logicalOffset);
+        LayoutUnit pageLogicalHeightAtNewOffset = hasUniformPageLogicalHeight ? pageLogicalHeight : pageLogicalHeightForOffset(logicalOffset + remainingLogicalHeight);
+        if (lineBox == firstRootBox() && totalLogicalHeight < pageLogicalHeightAtNewOffset && !isPositioned() && !isTableCell())
+            setPaginationStrut(remainingLogicalHeight + max<LayoutUnit>(0, logicalOffset));
+        else {
+            delta += remainingLogicalHeight;
+            lineBox->setPaginationStrut(remainingLogicalHeight);
+        }
+    }  
+}
+
+LayoutUnit RenderBlock::adjustBlockChildForPagination(LayoutUnit logicalTopAfterClear, LayoutUnit estimateWithoutPagination, RenderBox* child, bool atBeforeSideOfBlock)
+{
+    RenderBlock* childRenderBlock = child->isRenderBlock() ? toRenderBlock(child) : 0;
+
+    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);
+
+        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, false);
+        }
+        
+        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();
+    }
+
+    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);
+
+    // 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);
+    
+    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 && !isPositioned() && !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;
+    }
+
+    // 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;
+}
+
+bool RenderBlock::lineWidthForPaginatedLineChanged(RootInlineBox* rootBox, LayoutUnit lineDelta) const
+{
+    if (!inRenderFlowThread())
+        return false;
+
+    return rootBox->paginatedLineWidth() != availableLogicalWidthForContent(rootBox->lineTopWithLeading() + lineDelta);
+}
+
+LayoutUnit RenderBlock::offsetFromLogicalTopOfFirstPage() const
+{
+    // FIXME: This function needs to work without layout state. It's fine to use the layout state as a cache
+    // for speed, but we need a slow implementation that will walk up the containing block chain and figure
+    // out our offset from the top of the page.
+    LayoutState* layoutState = view()->layoutState();
+    if (!layoutState || !layoutState->isPaginated())
+        return 0;
+
+    // FIXME: Sanity check that the renderer in the layout state is ours, since otherwise the computation will be off.
+    // Right now this assert gets hit inside computeLogicalHeight for percentage margins, since they're computed using
+    // widths which can vary in each region. Until we patch that, we can't have this assert.
+    // ASSERT(layoutState->m_renderer == this);
+
+    LayoutSize offsetDelta = layoutState->m_layoutOffset - layoutState->m_pageOffset;
+    return isHorizontalWritingMode() ? offsetDelta.height() : offsetDelta.width();
+}
+
+RenderRegion* RenderBlock::regionAtBlockOffset(LayoutUnit blockOffset) const
+{
+    if (!inRenderFlowThread())
+        return 0;
+
+    RenderFlowThread* flowThread = enclosingRenderFlowThread();
+    if (!flowThread || !flowThread->hasValidRegionInfo())
+        return 0;
+
+    return flowThread->renderRegionForLine(offsetFromLogicalTopOfFirstPage() + blockOffset, true);
+}
+
+void RenderBlock::setStaticInlinePositionForChild(RenderBox* child, LayoutUnit blockOffset, LayoutUnit inlinePosition)
+{
+    if (inRenderFlowThread()) {
+        // Shift the inline position to exclude the region offset.
+        inlinePosition += startOffsetForContent() - startOffsetForContent(blockOffset);
+    }
+    child->layer()->setStaticInlinePosition(inlinePosition);
+}
+
+bool RenderBlock::logicalWidthChangedInRegions() const
+{
+    if (!inRenderFlowThread())
+        return false;
+    
+    RenderFlowThread* flowThread = enclosingRenderFlowThread();
+    if (!flowThread || !flowThread->hasValidRegionInfo())
+        return 0;
+    
+    return flowThread->logicalWidthChangedInRegions(this, offsetFromLogicalTopOfFirstPage());
+}
+
+RenderRegion* RenderBlock::clampToStartAndEndRegions(RenderRegion* region) const
+{
+    ASSERT(region && inRenderFlowThread());
+    
+    // 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;
+    enclosingRenderFlowThread()->getRegionRangeForBox(this, startRegion, endRegion);
+    
+    if (startRegion && region->offsetFromLogicalTopOfFirstPage() < startRegion->offsetFromLogicalTopOfFirstPage())
+        return startRegion;
+    if (endRegion && region->offsetFromLogicalTopOfFirstPage() > endRegion->offsetFromLogicalTopOfFirstPage())
+        return endRegion;
+    
+    return region;
+}
+
+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();
+    
+    // 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();
+    
+    // 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
+{
+    // If the child has the same directionality as we do, then we can just return its
+    // collapsed margin.
+    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();
+    
+    // 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);
+}
+
+LayoutUnit RenderBlock::marginBeforeForChild(const RenderBoxModelObject* child) const
+{
+    switch (style()->writingMode()) {
+    case TopToBottomWritingMode:
+        return child->marginTop();
+    case BottomToTopWritingMode:
+        return child->marginBottom();
+    case LeftToRightWritingMode:
+        return child->marginLeft();
+    case RightToLeftWritingMode:
+        return child->marginRight();
+    }
+    ASSERT_NOT_REACHED();
+    return child->marginTop();
+}
+
+LayoutUnit RenderBlock::marginAfterForChild(const RenderBoxModelObject* child) const
+{
+    switch (style()->writingMode()) {
+    case TopToBottomWritingMode:
+        return child->marginBottom();
+    case BottomToTopWritingMode:
+        return child->marginTop();
+    case LeftToRightWritingMode:
+        return child->marginRight();
+    case RightToLeftWritingMode:
+        return child->marginLeft();
+    }
+    ASSERT_NOT_REACHED();
+    return child->marginBottom();
+}
+
+LayoutUnit RenderBlock::marginLogicalLeftForChild(const RenderBoxModelObject* child) const
+{
+    if (isHorizontalWritingMode())
+        return child->marginLeft();
+    return child->marginTop();
+}
+
+LayoutUnit RenderBlock::marginLogicalRightForChild(const RenderBoxModelObject* child) const
+{
+    if (isHorizontalWritingMode())
+        return child->marginRight();
+    return child->marginBottom();
+}
+
+LayoutUnit RenderBlock::marginStartForChild(const RenderBoxModelObject* child) const
+{
+    if (isHorizontalWritingMode())
+        return style()->isLeftToRightDirection() ? child->marginLeft() : child->marginRight();
+    return style()->isLeftToRightDirection() ? child->marginTop() : child->marginBottom();
+}
+
+LayoutUnit RenderBlock::marginEndForChild(const RenderBoxModelObject* child) const
+{
+    if (isHorizontalWritingMode())
+        return style()->isLeftToRightDirection() ? child->marginRight() : child->marginLeft();
+    return style()->isLeftToRightDirection() ? child->marginBottom() : child->marginTop();
+}
+
+void RenderBlock::setMarginStartForChild(RenderBox* child, LayoutUnit margin)
+{
+    if (isHorizontalWritingMode()) {
+        if (style()->isLeftToRightDirection())
+            child->setMarginLeft(margin);
+        else
+            child->setMarginRight(margin);
+    } else {
+        if (style()->isLeftToRightDirection())
+            child->setMarginTop(margin);
+        else
+            child->setMarginBottom(margin);
+    }
+}
+
+void RenderBlock::setMarginEndForChild(RenderBox* child, LayoutUnit margin)
+{
+    if (isHorizontalWritingMode()) {
+        if (style()->isLeftToRightDirection())
+            child->setMarginRight(margin);
+        else
+            child->setMarginLeft(margin);
+    } else {
+        if (style()->isLeftToRightDirection())
+            child->setMarginBottom(margin);
+        else
+            child->setMarginTop(margin);
+    }
+}
+
+void RenderBlock::setMarginBeforeForChild(RenderBox* child, LayoutUnit margin)
+{
+    switch (style()->writingMode()) {
+    case TopToBottomWritingMode:
+        child->setMarginTop(margin);
+        break;
+    case BottomToTopWritingMode:
+        child->setMarginBottom(margin);
+        break;
+    case LeftToRightWritingMode:
+        child->setMarginLeft(margin);
+        break;
+    case RightToLeftWritingMode:
+        child->setMarginRight(margin);
+        break;
+    }
+}
+
+void RenderBlock::setMarginAfterForChild(RenderBox* child, LayoutUnit margin)
+{
+    switch (style()->writingMode()) {
+    case TopToBottomWritingMode:
+        child->setMarginBottom(margin);
+        break;
+    case BottomToTopWritingMode:
+        child->setMarginTop(margin);
+        break;
+    case LeftToRightWritingMode:
+        child->setMarginRight(margin);
+        break;
+    case RightToLeftWritingMode:
+        child->setMarginLeft(margin);
+        break;
+    }
+}
+
+RenderBlock::MarginValues RenderBlock::marginValuesForChild(RenderBox* child)
+{
+    int childBeforePositive = 0;
+    int childBeforeNegative = 0;
+    int childAfterPositive = 0;
+    int childAfterNegative = 0;
+
+    int beforeMargin = 0;
+    int 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 (isPositioned())
+        return "RenderBlock (positioned)";
+    if (isAnonymousColumnsBlock())
+        return "RenderBlock (anonymous multi-column)";
+    if (isAnonymousColumnSpanBlock())
+        return "RenderBlock (anonymous multi-column span)";
+    if (isAnonymousBlock())
+        return "RenderBlock (anonymous)";
+    else if (isAnonymous())
+        return "RenderBlock (generated)";
+    if (isRelPositioned())
+        return "RenderBlock (relative positioned)";
+    if (isRunIn())
+        return "RenderBlock (run-in)";
+    return "RenderBlock";
+}
+
+inline void RenderBlock::FloatingObjects::clear()
+{
+    m_set.clear();
+    m_placedFloatsTree.clear();
+    m_leftObjectsCount = 0;
+    m_rightObjectsCount = 0;
+    m_positionedObjectsCount = 0;
+}
+
+inline void RenderBlock::FloatingObjects::increaseObjectsCount(FloatingObject::Type type)
+{    
+    if (type == FloatingObject::FloatLeft)
+        m_leftObjectsCount++;
+    else if (type == FloatingObject::FloatRight)
+        m_rightObjectsCount++;
+    else
+        m_positionedObjectsCount++;
+}
+
+inline void RenderBlock::FloatingObjects::decreaseObjectsCount(FloatingObject::Type type)
+{
+    if (type == FloatingObject::FloatLeft)
+        m_leftObjectsCount--;
+    else if (type == FloatingObject::FloatRight)
+        m_rightObjectsCount--;
+    else
+        m_positionedObjectsCount--;
+}
+
+inline RenderBlock::FloatingObjectInterval RenderBlock::FloatingObjects::intervalForFloatingObject(FloatingObject* floatingObject)
+{
+    if (m_horizontalWritingMode)
+        return RenderBlock::FloatingObjectInterval(floatingObject->y(), floatingObject->maxY(), floatingObject);
+    return RenderBlock::FloatingObjectInterval(floatingObject->x(), floatingObject->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()
+{
+    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));
+    }
+}
+
+TextRun RenderBlock::constructTextRun(RenderObject* context, const Font& font, const UChar* characters, int length, RenderStyle* style, TextRun::ExpansionBehavior expansion, TextRunFlags flags)
+{
+    ASSERT(style);
+
+    TextDirection textDirection = LTR;
+    bool directionalOverride = style->rtlOrdering() == VisualOrder;
+    if (flags != DefaultTextRunFlags) {
+        if (flags & RespectDirection)
+            textDirection = style->direction();
+        if (flags & RespectDirectionOverride)
+            directionalOverride |= style->unicodeBidi() == Override;
+    }
+
+    TextRun run(characters, length, false, 0, 0, expansion, textDirection, directionalOverride);
+    if (textRunNeedsRenderingContext(font))
+        run.setRenderingContext(SVGTextRunRenderingContext::create(context));
+
+    return run;
+}
+
+TextRun RenderBlock::constructTextRun(RenderObject* context, const Font& font, const String& string, RenderStyle* style, TextRun::ExpansionBehavior expansion, TextRunFlags flags)
+{
+    return constructTextRun(context, font, string.characters(), string.length(), style, expansion, flags);
+}
+
+#ifndef NDEBUG
+
+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);
+}
+
+String ValueToString<RenderBlock::FloatingObject*>::string(const RenderBlock::FloatingObject* floatingObject)
+{
+    return String::format("%p (%dx%d %dx%d)", floatingObject, floatingObject->x(), floatingObject->y(), floatingObject->maxX(), floatingObject->maxY());
+}
+
+#endif
+
+} // namespace WebCore