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

content/browser/renderer_host/backing_store_skia.cc

Index: content/browser/renderer_host/backing_store_skia.cc
diff --git a/content/browser/renderer_host/backing_store_skia.cc b/content/browser/renderer_host/backing_store_skia.cc
index 300e4fe9cc736498a372b4646107010bb9d5e636..17e6e909455ba84a2f8f830e031598a980e356fb 100644
--- a/content/browser/renderer_host/backing_store_skia.cc
+++ b/content/browser/renderer_host/backing_store_skia.cc
@@ -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.
 
@@ -30,7 +30,7 @@ BackingStoreSkia::~BackingStoreSkia() {
 }
 
 void BackingStoreSkia::SkiaShowRect(const gfx::Point& point,
-                                    gfx::Canvas* canvas) {
+                                    gfx::CanvasSkia* canvas) {
   canvas->GetSkCanvas()->drawBitmap(bitmap_,
       SkIntToScalar(point.x()), SkIntToScalar(point.y()));
 }