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

ash/app_list/drop_shadow_label.h

Index: ash/app_list/drop_shadow_label.h
diff --git a/ash/app_list/drop_shadow_label.h b/ash/app_list/drop_shadow_label.h
index 2a7ce5d55be347df9d79e93f47f4f3ca9fea3772..9ab4bfefb29ba8fc6ba59b1aba1159e79a8c9a59 100644
--- a/ash/app_list/drop_shadow_label.h
+++ b/ash/app_list/drop_shadow_label.h
@@ -1,4 +1,4 @@
-// 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.
 
@@ -35,7 +35,7 @@ class DropShadowLabel : public views::Label  {
   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;