Add window overview mode behind --ash-enable-overview-mode flag to F5 key.

ash/wm/window_selector.h

Index: ash/wm/window_selector.h
diff --git a/ash/wm/window_selector.h b/ash/wm/window_selector.h
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+++ b/ash/wm/window_selector.h
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+// Copyright (c) 2013 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_WINDOW_SELECTOR_H_
+#define ASH_WM_WINDOW_SELECTOR_H_
+
+#include <vector>
+
+#include "base/compiler_specific.h"
+#include "ui/aura/window_observer.h"
+#include "ui/base/events/event_handler.h"
+
+namespace aura {
+class RootWindow;
+}
+
+namespace ash {
+
+class WindowSelectorDelegate;
+
+// The WindowSelector shows a grid of all of your windows and allows selecting
+// a window by clicking or tapping on it.
+class WindowSelector : public ui::EventHandler,
+                       public aura::WindowObserver {
+ public:
+  typedef std::vector<aura::Window*> WindowList;
+
+  WindowSelector(const WindowList& windows,
+                 WindowSelectorDelegate* delegate);
+  virtual ~WindowSelector();
+
+  // ui::EventHandler:
+  virtual void OnEvent(ui::Event* event) OVERRIDE;
+  virtual void OnMouseEvent(ui::MouseEvent* event) OVERRIDE;
+  virtual void OnGestureEvent(ui::GestureEvent* event) OVERRIDE;
+
+  // aura::WindowObserver:
+  virtual void OnWindowDestroyed(aura::Window* window) OVERRIDE;
+
+ private:
+  void HandleSelectionEvent(ui::Event* event);
+  void PositionWindows();
+  void PositionWindowsOnRoot(aura::RootWindow* root_window,
+                             const WindowList& windows);
+
+  void SelectWindow(aura::Window*);
+
+  // List of weak pointers of windows to select from.
+  WindowList windows_;
+
+  // Weak pointer to the selector delegate which will be called when a
+  // selection is made.
+  WindowSelectorDelegate* delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(WindowSelector);
+};
+
+}  // namespace ash
+
+#endif  // ASH_WM_WINDOW_SELECTOR_H_