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

content/browser/renderer_host/backing_store_skia.h

-// 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_BACKING_STORE_SKIA_H_
 #define CONTENT_BROWSER_RENDERER_HOST_BACKING_STORE_SKIA_H_
 #pragma once
 
 #include "base/memory/scoped_ptr.h"
 #include "content/browser/renderer_host/backing_store.h"
 #include "content/common/content_export.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 
 class SkCanvas;
 
 namespace gfx {
 class Point;
-class Canvas;
+class CanvasSkia;
 }
 
 namespace content {
 class RenderProcessHost;
 }
 
 // A backing store that uses skia. This is a temporary backing store used by
 // RenderWidgetHostViewViews. In time, only GPU rendering will be used for
 // RWHVV, and then this backing store will be removed.
 class BackingStoreSkia : public BackingStore {
  public:
   CONTENT_EXPORT BackingStoreSkia(
       RenderWidgetHost* widget,
       const gfx::Size& size);
 
   virtual ~BackingStoreSkia();
 
   CONTENT_EXPORT void SkiaShowRect(const gfx::Point& point,
-                                   gfx::Canvas* canvas);
+                                   gfx::CanvasSkia* canvas);
 
   // BackingStore implementation.
   virtual size_t MemorySize() OVERRIDE;
   virtual void PaintToBackingStore(
       content::RenderProcessHost* process,
       TransportDIB::Id bitmap,
       const gfx::Rect& bitmap_rect,
       const std::vector<gfx::Rect>& copy_rects,
       const base::Closure& completion_callback,
       bool* scheduled_completion_callback) OVERRIDE;
   virtual bool CopyFromBackingStore(const gfx::Rect& rect,
                                     skia::PlatformCanvas* output) OVERRIDE;
   virtual void ScrollBackingStore(int dx, int dy,
                                   const gfx::Rect& clip_rect,
                                   const gfx::Size& view_size) OVERRIDE;
 
  private:
   SkBitmap bitmap_;
 
   scoped_ptr<SkCanvas> canvas_;
 
   DISALLOW_COPY_AND_ASSIGN(BackingStoreSkia);
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_BACKING_STORE_SKIA_H_