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

content/browser/renderer_host/backing_store_skia.h

Index: content/browser/renderer_host/backing_store_skia.h
diff --git a/content/browser/renderer_host/backing_store_skia.h b/content/browser/renderer_host/backing_store_skia.h
index b713a849b76b159e1bb4e4ba12e2dd33846133dc..55e87185a61b25739ae6758c8f84c0f73d008d92 100644
--- a/content/browser/renderer_host/backing_store_skia.h
+++ b/content/browser/renderer_host/backing_store_skia.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.
 
@@ -15,7 +15,7 @@ class SkCanvas;
 
 namespace gfx {
 class Point;
-class Canvas;
+class CanvasSkia;
 }
 
 namespace content {
@@ -34,7 +34,7 @@ class BackingStoreSkia : public BackingStore {
   virtual ~BackingStoreSkia();
 
   CONTENT_EXPORT void SkiaShowRect(const gfx::Point& point,
-                                   gfx::Canvas* canvas);
+                                   gfx::CanvasSkia* canvas);
 
   // BackingStore implementation.
   virtual size_t MemorySize() OVERRIDE;