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

ui/views/native_theme_painter.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_VIEWS_NATIVE_THEME_PAINTER_H_
 #define UI_VIEWS_NATIVE_THEME_PAINTER_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "ui/views/painter.h"
 
 namespace gfx {
-class Canvas;
+class CanvasSkia;
 class Size;
 }
 
 namespace views {
 
 class NativeThemeDelegate;
 
 // A Painter that uses NativeTheme to implement painting and sizing.  A
 // theme delegate must be given at construction time so that the appropriate
 // painting and sizing can be done.
 class VIEWS_EXPORT NativeThemePainter : public Painter {
  public:
   explicit NativeThemePainter(NativeThemeDelegate* delegate);
 
   virtual ~NativeThemePainter() {}
 
   // Returns the preferred size of the native part being painted.
   gfx::Size GetPreferredSize();
 
  private:
   // The delegate the controls the appearance of this painter.
   NativeThemeDelegate* delegate_;
 
   // Overridden from Painter:
-  virtual void Paint(gfx::Canvas* canvas, const gfx::Size& size) OVERRIDE;
+  virtual void Paint(gfx::CanvasSkia* canvas, const gfx::Size& size) OVERRIDE;
 
   DISALLOW_COPY_AND_ASSIGN(NativeThemePainter);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_NATIVE_THEME_PAINTER_H_