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

ui/gfx/compositor/layer_delegate.h

Index: ui/gfx/compositor/layer_delegate.h
diff --git a/ui/gfx/compositor/layer_delegate.h b/ui/gfx/compositor/layer_delegate.h
index 1f494b13459ac9a20d77d56c9608c0ea2ed850ce..2dcc269ef3a840031d873d2d6ed909e4614dc0de 100644
--- a/ui/gfx/compositor/layer_delegate.h
+++ b/ui/gfx/compositor/layer_delegate.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.
 
@@ -9,7 +9,7 @@
 #include "ui/gfx/compositor/compositor_export.h"
 
 namespace gfx {
-class Canvas;
+class CanvasSkia;
 }
 
 namespace ui {
@@ -19,7 +19,7 @@ class COMPOSITOR_EXPORT LayerDelegate {
  public:
   // Paint content for the layer to the specified canvas. It has already been
   // clipped to the Layer's invalid rect.
-  virtual void OnPaintLayer(gfx::Canvas* canvas) = 0;
+  virtual void OnPaintLayer(gfx::CanvasSkia* canvas) = 0;
 
  protected:
   virtual ~LayerDelegate() {}