Make GetRootWindow() return a Window instead of a RootWindow.

ash/scoped_target_root_window.h

 // Copyright 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_SCOPED_TARGET_ROOT_WINDOW_H_
 #define ASH_SCOPED_TARGET_ROOT_WINDOW_H_
 
 #include "base/basictypes.h"
 
 namespace aura {
-class RootWindow;
+class Window;
 }
 
 namespace ash {
 namespace internal {
 
 // Constructing a ScopedTargetRootWindow allows temporarily
 // switching a target root window so that a new window gets created
 // in the same window where a user interaction happened.
 // An example usage is to specify the target root window when creating
 // a new window using launcher's icon.
 class ScopedTargetRootWindow {
  public:
-  explicit ScopedTargetRootWindow(aura::RootWindow* root_window);
+  explicit ScopedTargetRootWindow(aura::Window* root_window);
   ~ScopedTargetRootWindow();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ScopedTargetRootWindow);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SCOPED_TARGET_ROOT_WINDOW_H_