Add support for writing raw encoder output to .ivf files.

webrtc/video/video_receive_stream.h

Index: webrtc/video/video_receive_stream.h
diff --git a/webrtc/video/video_receive_stream.h b/webrtc/video/video_receive_stream.h
index 3aca570f99e9d3a96d19a0abc2f56f547029cd44..d507a9b4e645a3c697eae00310a50b467f942a38 100644
--- a/webrtc/video/video_receive_stream.h
+++ b/webrtc/video/video_receive_stream.h
@@ -31,6 +31,7 @@ namespace webrtc {
 
 class CallStats;
 class CongestionController;
+class IvfFileWriter;
 class ProcessThread;
 class VoiceEngine;
 class VieRemb;
@@ -110,6 +111,8 @@ class VideoReceiveStream : public webrtc::VideoReceiveStream,
   ViEReceiver* const vie_receiver_;
   ViESyncModule vie_sync_;
   RtpRtcp* const rtp_rtcp_;
+
+  std::unique_ptr<IvfFileWriter> ivf_writer_;
 };
 }  // namespace internal
 }  // namespace webrtc