Make aura::clients take Window instead of RootWindow

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"
 
 namespace ui {
 class Event;
 }
 
 namespace aura {
-class RootWindow;
 class Window;
-
 namespace client {
 class FocusChangeObserver;
 
 // An interface implemented by an object that manages window focus.
 class AURA_EXPORT FocusClient {
  public:
   virtual ~FocusClient() {}
 
   virtual void AddObserver(FocusChangeObserver* observer) = 0;
   virtual void RemoveObserver(FocusChangeObserver* observer) = 0;
 
   // Focuses |window|. Passing NULL clears focus.
   virtual void FocusWindow(Window* window) = 0;
 
   // Sets focus to |window| if it's within the active window. Not intended as a
   // general purpose API, use FocusWindow() instead.
   virtual void ResetFocusWithinActiveWindow(Window* window) = 0;
 
   // Retrieves the focused window, or NULL if there is none.
   virtual Window* GetFocusedWindow() = 0;
 };
 
-// Sets/Gets the focus client on the RootWindow.
-AURA_EXPORT void SetFocusClient(RootWindow* root_window, FocusClient* client);
+// 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);
 
 }  // namespace clients
 }  // namespace aura
 
 #endif  // UI_AURA_CLIENT_FOCUS_CLIENT_H_