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

ui/views/background.h

Index: ui/views/background.h
diff --git a/ui/views/background.h b/ui/views/background.h
index 64f609c0f59761fd26a8d2f980975c719e00454c..d9a8c6e09c3c0b2881f0c3d8b42b41a58d545e02 100644
--- a/ui/views/background.h
+++ b/ui/views/background.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.
 
@@ -17,7 +17,7 @@
 #include "ui/views/views_export.h"
 
 namespace gfx {
-class Canvas;
+class CanvasSkia;
 }
 
 namespace views {
@@ -69,7 +69,7 @@ class VIEWS_EXPORT Background {
                                              Painter* painter);
 
   // Render the background for the provided view
-  virtual void Paint(gfx::Canvas* canvas, View* view) const = 0;
+  virtual void Paint(gfx::CanvasSkia* canvas, View* view) const = 0;
 
   // Set a solid, opaque color to be used when drawing backgrounds of native
   // controls.  Unfortunately alpha=0 is not an option.