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

ash/shelf/shelf_layout_manager.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_SHELF_SHELF_LAYOUT_MANAGER_H_
 #define ASH_SHELF_SHELF_LAYOUT_MANAGER_H_
 
 #include <vector>
 
 #include "ash/ash_export.h"
@@ skipping 324 matching lines @@
   virtual void OnDockBoundsChanging(
       const gfx::Rect& dock_bounds,
       DockedWindowLayoutManagerObserver::Reason reason) OVERRIDE;
 
   // Generates insets for inward edge based on the current shelf alignment.
   gfx::Insets GetInsetsForAlignment(int distance) const;
 
   // The RootWindow is cached so that we don't invoke Shell::GetInstance() from
   // our destructor. We avoid that as at the time we're deleted Shell is being
   // deleted too.
-  aura::RootWindow* root_window_;
+  aura::Window* root_window_;
 
   // True when inside UpdateBoundsAndOpacity() method. Used to prevent calling
   // UpdateBoundsAndOpacity() again from SetChildBounds().
   bool updating_bounds_;
 
   // See description above setter.
   ShelfAutoHideBehavior auto_hide_behavior_;
 
   // See description above getter.
   ShelfAlignment alignment_;
@@ skipping 51 matching lines @@
   // The bounds of the dock.
   gfx::Rect dock_bounds_;
 
   DISALLOW_COPY_AND_ASSIGN(ShelfLayoutManager);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SHELF_SHELF_LAYOUT_MANAGER_H_