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

ash/shelf/shelf_alignment_menu.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_SHELF_SHELF_ALIGNMENT_MENU_H_
 #define ASH_SHELF_SHELF_ALIGNMENT_MENU_H_
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "ui/base/models/simple_menu_model.h"
 
 namespace aura {
 class RootWindow;
 }
 
 namespace ash {
 
 // Submenu for choosing the alignment of the launcher.
 class ASH_EXPORT ShelfAlignmentMenu : public ui::SimpleMenuModel,
                                       public ui::SimpleMenuModel::Delegate {
  public:
-  explicit ShelfAlignmentMenu(aura::RootWindow* root);
+  explicit ShelfAlignmentMenu(aura::Window* root);
   virtual ~ShelfAlignmentMenu();
 
   // ui::SimpleMenuModel::Delegate overrides:
   virtual bool IsCommandIdChecked(int command_id) const OVERRIDE;
   virtual bool IsCommandIdEnabled(int command_id) const OVERRIDE;
   virtual bool GetAcceleratorForCommandId(
       int command_id,
       ui::Accelerator* accelerator) OVERRIDE;
   virtual void ExecuteCommand(int command_id, int event_flags) OVERRIDE;
 
  private:
   enum MenuItem {
     // Offset so as not to interfere with other menus.
     MENU_ALIGN_LEFT = 500,
     MENU_ALIGN_RIGHT,
     MENU_ALIGN_BOTTOM,
   };
 
-  aura::RootWindow* root_window_;
+  aura::Window* root_window_;
 
   DISALLOW_COPY_AND_ASSIGN(ShelfAlignmentMenu);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELF_SHELF_ALIGNMENT_MENU_H_