Split Screen mode implementation.

athena/wm/mru_window_tracker.h

Index: athena/wm/mru_window_tracker.h
diff --git a/athena/wm/mru_window_tracker.h b/athena/wm/mru_window_tracker.h
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+// Copyright 2014 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 ATHENA_WM_MRU_WINDOW_TRACKER_H_
+#define ATHENA_WM_MRU_WINDOW_TRACKER_H_
+
+#include <list>
+
+#include "athena/wm/public/window_list_provider.h"
+#include "ui/aura/window_observer.h"
+
+namespace aura {
+class Window;
+}
+
+namespace athena {
+
+// Maintains a most recently used list of windows. This is used for window
+// cycling and overview mode.
+class MruWindowTracker : public WindowListProvider,
+                         public aura::WindowObserver {
+ public:
+  explicit MruWindowTracker(aura::Window* container);
+  virtual ~MruWindowTracker();
+
+  // Overridden from WindowListProvider
+  virtual aura::Window::Windows GetWindowList() const OVERRIDE;
+
+  // Updates the mru_windows_ list to move |window| to the front.
+  // |window| must be the child of |container_|.
+  virtual void MoveToFront(aura::Window* window) OVERRIDE;
+
+ private:
+  // Overridden from WindowObserver:
+  virtual void OnWillRemoveWindow(aura::Window* window) OVERRIDE;
+  virtual void OnWindowAdded(aura::Window* new_window) OVERRIDE;
+
+  // List of windows that have been used in the container, sorted by most
+  // recently used.
+  std::list<aura::Window*> mru_windows_;
+  aura::Window* container_;
+
+  DISALLOW_COPY_AND_ASSIGN(MruWindowTracker);
+};
+
+}  // namespace athena
+
+#endif  // ATHENA_WM_MRU_WINDOW_TRACKER_H_