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

ui/views/controls/menu/menu_separator.h

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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_VIEWS_CONTROLS_MENU_MENU_SEPARATOR_H_
 #define UI_VIEWS_CONTROLS_MENU_MENU_SEPARATOR_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "ui/views/view.h"
 
 namespace views {
 
 class MenuSeparator : public View {
  public:
   MenuSeparator() {}
 
   // View overrides.
-  virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
+  virtual void OnPaint(gfx::CanvasSkia* canvas) OVERRIDE;
   virtual gfx::Size GetPreferredSize() OVERRIDE;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MenuSeparator);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_MENU_MENU_SEPARATOR_H_