Change FocusSynchronizer to maintain active focus client and window.

ui/aura/client/focus_client.h

 // 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 UI_AURA_CLIENT_FOCUS_CLIENT_H_
 #define UI_AURA_CLIENT_FOCUS_CLIENT_H_
 
 #include "ui/aura/aura_export.h"
 #include "ui/aura/window.h"
 
@@ skipping 18 matching lines @@
 
   // Retrieves the focused window, or NULL if there is none.
   virtual Window* GetFocusedWindow() = 0;
 };
 
 // Sets/Gets the focus client on the root Window.
 AURA_EXPORT void SetFocusClient(Window* root_window, FocusClient* client);
 AURA_EXPORT FocusClient* GetFocusClient(Window* window);
 AURA_EXPORT FocusClient* GetFocusClient(const Window* window);
 
-// The focus client is stored on the window using this property.
-AURA_EXPORT extern const WindowProperty<FocusClient*>* const kFocusClientKey;
-
 }  // namespace clients
 }  // namespace aura
 
 #endif  // UI_AURA_CLIENT_FOCUS_CLIENT_H_