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

ash/app_list/drop_shadow_label.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 ASH_APP_LIST_DROP_SHADOW_LABEL_H_
 #define ASH_APP_LIST_DROP_SHADOW_LABEL_H_
 #pragma once
 
 #include "ui/gfx/font.h"
 #include "ui/views/controls/label.h"
 
@@ skipping 16 matching lines @@
   // shadow -- it gets more expensive to draw the larger it gets,
   // since it simply draws more copies of the string.  For instance,
   // for a value of two, the string is draw seven times.  In general,
   // it is drawn three extra times for each increment of |size|.
   void SetDropShadowSize(int size);
 
   // Return the size of the drop shadow in pixels.
   int drop_shadow_size() const { return drop_shadow_size_; }
 
   // Overridden to paint the text differently from the base class.
-  virtual void PaintText(gfx::Canvas* canvas,
+  virtual void PaintText(gfx::CanvasSkia* canvas,
                          const string16& text,
                          const gfx::Rect& text_bounds,
                          int flags) OVERRIDE;
 
  protected:
   virtual gfx::Size GetTextSize() const OVERRIDE;
 
  private:
   int drop_shadow_size_;
 
   DISALLOW_COPY_AND_ASSIGN(DropShadowLabel);
 };
 
 }  // namespace ash
 
 #endif  // ASH_APP_LIST_DROP_SHADOW_LABEL_H_