ui/gfx: Make gfx::Canvas inherit from gfx::CanvasSkia.

ui/aura/window.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_WINDOW_H_
 #define UI_AURA_WINDOW_H_
 #pragma once
 
 #include <map>
 #include <string>
@@ skipping 336 matching lines @@
 
   // Called when this window's stacking order among its siblings is changed.
   void OnStackingChanged();
 
   // Notifies observers registered with this Window (and its subtree) when the
   // Window has been added or is about to be removed from a RootWindow.
   void NotifyAddedToRootWindow();
   void NotifyRemovingFromRootWindow();
 
   // Overridden from ui::LayerDelegate:
-  virtual void OnPaintLayer(gfx::Canvas* canvas) OVERRIDE;
+  virtual void OnPaintLayer(gfx::CanvasSkia* canvas) OVERRIDE;
 
   // Updates the layer name with a name based on the window's name and id.
   void UpdateLayerName(const std::string& name);
 
   // Returns true if this window is behind a window that stops event
   // propagation.
   bool IsBehindStopEventsWindow() const;
 
   client::WindowType type_;
 
@@ skipping 46 matching lines @@
   ObserverList<WindowObserver> observers_;
 
   std::map<const void*, intptr_t> prop_map_;
 
   DISALLOW_COPY_AND_ASSIGN(Window);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_H_