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diff --git a/chromium/ash/wm/overlay_event_filter.h b/chromium/ash/wm/overlay_event_filter.h
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+++ b/chromium/ash/wm/overlay_event_filter.h
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+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_WM_OVERLAY_EVENT_FILTER_H_
+#define ASH_WM_OVERLAY_EVENT_FILTER_H_
+
+#include "ash/shell_observer.h"
+#include "base/compiler_specific.h"
+#include "ui/aura/window.h"
+#include "ui/base/events/event_handler.h"
+
+namespace ash {
+namespace internal {
+
+// EventFilter for the "overlay window", which intercepts events before they are
+// processed by the usual path (e.g. the partial screenshot UI, the keyboard
+// overlay).  It does nothing the first time, but works when |Activate()| is
+// called.  The main task of this event filter is just to stop propagation
+// of any key events during activation, and also signal cancellation when keys
+// for canceling are pressed.
+class OverlayEventFilter : public ui::EventHandler,
+                           public ShellObserver {
+ public:
+  // Windows that need to receive events from OverlayEventFilter implement this.
+  class Delegate {
+   public:
+    // Invoked when OverlayEventFilter needs to stop handling events.
+    virtual void Cancel() = 0;
+
+    // Returns true if the overlay should be canceled in response to |event|.
+    virtual bool IsCancelingKeyEvent(ui::KeyEvent* event) = 0;
+
+    // Returns the window that needs to receive events. NULL if no window needs
+    // to receive key events from OverlayEventFilter.
+    virtual aura::Window* GetWindow() = 0;
+  };
+
+  OverlayEventFilter();
+  virtual ~OverlayEventFilter();
+
+  // Starts the filtering of events.  It also notifies the specified
+  // |delegate| when a key event means cancel (like Esc).  It holds the
+  // pointer to the specified |delegate| until Deactivate() is called, but
+  // does not take ownership.
+  void Activate(Delegate* delegate);
+
+  // Ends the filtering of events.
+  void Deactivate();
+
+  // Cancels the partial screenshot UI.  Do nothing if it's not activated.
+  void Cancel();
+
+  // ui::EventHandler overrides:
+  virtual void OnKeyEvent(ui::KeyEvent* event) OVERRIDE;
+
+  // ShellObserver overrides:
+  virtual void OnLoginStateChanged(user::LoginStatus status) OVERRIDE;
+  virtual void OnAppTerminating() OVERRIDE;
+  virtual void OnLockStateChanged(bool locked) OVERRIDE;
+
+ private:
+  Delegate* delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(OverlayEventFilter);
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_WM_OVERLAY_EVENT_FILTER_H_