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

ash/wm/coordinate_conversion.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 ASH_WM_COORDINATE_CONVERSION_H_
 #define ASH_WM_COORDINATE_CONVERSION_H_
 
 #include "ash/ash_export.h"
 
 namespace aura {
-class RootWindow;
 class Window;
 }  // namespace gfx
 
 namespace gfx {
 class Point;
 class Rect;
 }  // namespace gfx
 
 namespace ash {
 namespace wm {
 
 // Returns the RootWindow at |point| in the virtual screen coordinates.
 // Returns NULL if the root window does not exist at the given
 // point.
-ASH_EXPORT aura::RootWindow* GetRootWindowAt(const gfx::Point& point);
+ASH_EXPORT aura::Window* GetRootWindowAt(const gfx::Point& point);
 
 // Returns the RootWindow that shares the most area with |rect| in
 // the virtual scren coordinates.
-ASH_EXPORT aura::RootWindow* GetRootWindowMatching(const gfx::Rect& rect);
+ASH_EXPORT aura::Window* GetRootWindowMatching(const gfx::Rect& rect);
 
 // Converts the |point| from a given |window|'s coordinates into the screen
 // coordinates.
 ASH_EXPORT void ConvertPointToScreen(aura::Window* window, gfx::Point* point);
 
 // Converts the |point| from the screen coordinates to a given |window|'s
 // coordinates.
 ASH_EXPORT void ConvertPointFromScreen(aura::Window* window,
                                        gfx::Point* point_in_screen);
 
 }  // namespace wm
 }  // namespace ash
 
 #endif  // ASH_WM_COORDINATE_CONVERSION_H_