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

ui/views/controls/button/image_button.h

Index: ui/views/controls/button/image_button.h
diff --git a/ui/views/controls/button/image_button.h b/ui/views/controls/button/image_button.h
index 13116f3c6c36cbcee13dda472cdec1829db1b0d3..79cf5dc1d1d7503dbb9187f0c8a1ce4eace532f0 100644
--- a/ui/views/controls/button/image_button.h
+++ b/ui/views/controls/button/image_button.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.
 
@@ -44,7 +44,7 @@ class VIEWS_EXPORT ImageButton : public CustomButton {
 
   // Overridden from View:
   virtual gfx::Size GetPreferredSize() OVERRIDE;
-  virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
+  virtual void OnPaint(gfx::CanvasSkia* canvas) OVERRIDE;
 
   // Sets preferred size, so it could be correctly positioned in layout even if
   // it is NULL.