Add cricket::VideoFrame::frame_id() and set it to RTP timestamp.

webrtc/media/engine/webrtcvideoengine2.cc

 /*
  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 2451 matching lines @@
     estimated_remote_start_ntp_time_ms_ = frame.ntp_time_ms() - elapsed_time_ms;
 
   if (sink_ == NULL) {
     LOG(LS_WARNING) << "VideoReceiveStream not connected to a VideoSink.";
     return;
   }
 
   last_width_ = frame.width();
   last_height_ = frame.height();
 
-  const WebRtcVideoFrame render_frame(
+  WebRtcVideoFrame render_frame(
       frame.video_frame_buffer(), frame.rotation(),
-      frame.render_time_ms() * rtc::kNumNanosecsPerMicrosec);
+      frame.render_time_ms() * rtc::kNumNanosecsPerMicrosec, frame.timestamp());
   sink_->OnFrame(render_frame);
 }
 
 bool WebRtcVideoChannel2::WebRtcVideoReceiveStream::IsDefaultStream() const {
   return default_stream_;
 }
 
 void WebRtcVideoChannel2::WebRtcVideoReceiveStream::SetSink(
     rtc::VideoSinkInterface<cricket::VideoFrame>* sink) {
   rtc::CritScope crit(&sink_lock_);
@@ skipping 166 matching lines @@
         rtx_mapping[video_codecs[i].codec.id] !=
             fec_settings.red_payload_type) {
       video_codecs[i].rtx_payload_type = rtx_mapping[video_codecs[i].codec.id];
     }
   }
 
   return video_codecs;
 }
 
 }  // namespace cricket