Use webrtc::DesktopCapturer for screen capturer implementation.

media/video/capture/screen/shared_desktop_frame.h

Index: media/video/capture/screen/shared_desktop_frame.h
diff --git a/media/video/capture/screen/shared_desktop_frame.h b/media/video/capture/screen/shared_desktop_frame.h
new file mode 100644
index 0000000000000000000000000000000000000000..861b5f0411853a82f15e9269f3f7c4da94cb54c8
--- /dev/null
+++ b/media/video/capture/screen/shared_desktop_frame.h
@@ -0,0 +1,43 @@
+// Copyright 2013 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 MEDIA_VIDEO_CAPTURE_SCREEN_SHARED_DESKTOP_FRAME_H_
+#define MEDIA_VIDEO_CAPTURE_SCREEN_SHARED_DESKTOP_FRAME_H_
+
+#include "base/memory/ref_counted.h"
+#include "third_party/webrtc/modules/desktop_capture/desktop_frame.h"
+
+namespace media {
+
+// SharedDesktopFrame is a DesktopFrame that may have multiple instances all
+// sharing the same buffer.
+class SharedDesktopFrame : public webrtc::DesktopFrame {
+ public:
+  virtual ~SharedDesktopFrame();
+
+  static SharedDesktopFrame* Wrap(webrtc::DesktopFrame* desktop_frame);
+
+  // Returns the underlying instance of DesktopFrame.
+  webrtc::DesktopFrame* GetUnderlyingFrame();
+
+  // Creates a clone of this object.
+  SharedDesktopFrame* Share();
+
+  // Checks if the frame is currently shared. If it returns false it's
+  // guaranteed that there are no clones of the object.
+  bool IsShared();
+
+ private:
+  class Core;
+
+  SharedDesktopFrame(scoped_refptr<Core> core);
+
+  scoped_refptr<Core> core_;
+
+  DISALLOW_COPY_AND_ASSIGN(SharedDesktopFrame);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_VIDEO_CAPTURE_SCREEN_SHARED_DESKTOP_FRAME_H_