[Aura] Support transparent webkit.

content/browser/renderer_host/backing_store_skia.h

 // Copyright (c) 2011 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"
+#include "third_party/skia/include/core/SkPaint.h"
 
 class SkCanvas;
 
 namespace gfx {
 class Point;
 class Canvas;
 }
 
 // A backing store that uses skia. This is a temporary backing store used by
 // RenderWidgetHostViewViews. In time, only GPU rendering will be used for
@@ skipping 20 matching lines @@
                                     skia::PlatformCanvas* output);
   virtual void ScrollBackingStore(int dx, int dy,
                                   const gfx::Rect& clip_rect,
                                   const gfx::Size& view_size);
 
  private:
   SkBitmap bitmap_;
 
   scoped_ptr<SkCanvas> canvas_;
 
+  SkPaint copy_paint_;
+
   DISALLOW_COPY_AND_ASSIGN(BackingStoreSkia);
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_BACKING_STORE_SKIA_H_