Share backing canvases between browser compositors.

content/browser/compositor/software_output_device_win.h

 // Copyright 2014 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_COMPOSITOR_SOFTWARE_OUTPUT_DEVICE_WIN_H_
 #define CONTENT_BROWSER_COMPOSITOR_SOFTWARE_OUTPUT_DEVICE_WIN_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/output/software_output_device.h"
 
 #include <windows.h>
 
 namespace gfx {
 class Canvas;
 }
 
 namespace ui {
 class Compositor;
 }
 
 namespace content {
-
 class SoftwareOutputDeviceWin : public cc::SoftwareOutputDevice {
  public:
   explicit SoftwareOutputDeviceWin(ui::Compositor* compositor);
   ~SoftwareOutputDeviceWin() override;
 
   void Resize(const gfx::Size& viewport_pixel_size,
               float scale_factor) override;
   SkCanvas* BeginPaint(const gfx::Rect& damage_rect) override;
   void EndPaint(cc::SoftwareFrameData* frame_data) override;
 
+  gfx::Size viewport_pixel_size() const { return viewport_pixel_size_; }
+  void ReleaseContents();
+
  private:
   HWND hwnd_;
-  BITMAPINFO bitmap_info_;
-  scoped_ptr<gfx::Canvas> contents_;
+  scoped_ptr<SkCanvas> contents_;
   bool is_hwnd_composited_;
 
   DISALLOW_COPY_AND_ASSIGN(SoftwareOutputDeviceWin);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_COMPOSITOR_SOFTWARE_OUTPUT_DEVICE_WIN_H_