Add GetFrameConsumer() in VideoRenderer.

remoting/protocol/video_renderer.h

 // Copyright 2016 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 REMOTING_CLIENT_VIDEO_RENDERER_H_
 #define REMOTING_CLIENT_VIDEO_RENDERER_H_
 
 namespace remoting {
 namespace protocol {
 
+class FrameConsumer;
 class SessionConfig;
 class VideoStub;
 
 // VideoRenderer is responsible for decoding and displaying incoming video
-// stream.
+// stream. This interface is used by ConnectionToHost implementations to
+// render received video frames. ConnectionToHost may feed encoded frames to the
+// VideoStub or decode them and pass decoded frames to the FrameConsumer.
+//
+// TODO(sergeyu): Reconsider this design.
 class VideoRenderer {
  public:
   virtual ~VideoRenderer() {}
 
   // Configures the renderer with the supplied |config|. This must be called
   // exactly once before video data is supplied to the renderer.
   virtual void OnSessionConfig(const SessionConfig& config) = 0;
 
   // Returns the VideoStub interface of this renderer.
   virtual VideoStub* GetVideoStub() = 0;
+
+  // Returns the FrameConsumer interface for this renderer.
+  virtual FrameConsumer* GetFrameConsumer() = 0;
 };
 
 }  // namespace protocol;
 }  // namespace remoting
 
 #endif  // REMOTING_CLIENT_VIDEO_RENDERER_H_