Add histogram stats for AV sync stream offset:

webrtc/video/video_receive_stream.cc

 /*
  *  Copyright (c) 2013 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 366 matching lines @@
 
   // Post processing is not supported if the frame is backed by a texture.
   if (video_frame->native_handle() == NULL) {
     if (config_.pre_render_callback)
       config_.pre_render_callback->FrameCallback(video_frame);
   }
 }
 
 int VideoReceiveStream::RenderFrame(const uint32_t /*stream_id*/,
                                     const VideoFrame& video_frame) {
+  int64_t sync_offset_ms;
+  if (vie_sync_.GetStreamSyncOffsetInMs(video_frame, &sync_offset_ms))
+    stats_proxy_.OnSyncOffsetUpdated(sync_offset_ms);
+
   // TODO(pbos): Wire up config_.render->IsTextureSupported() and convert if not
   // supported. Or provide methods for converting a texture frame in
   // VideoFrame.
 
   if (config_.renderer != nullptr)
     config_.renderer->RenderFrame(
         video_frame,
         video_frame.render_time_ms() - clock_->TimeInMilliseconds());
 
   stats_proxy_.OnRenderedFrame(video_frame);
@@ skipping 35 matching lines @@
     const std::vector<uint16_t>& sequence_numbers) {
   rtp_rtcp_->SendNack(sequence_numbers);
 }
 
 void VideoReceiveStream::RequestKeyFrame() {
   rtp_rtcp_->RequestKeyFrame();
 }
 
 }  // namespace internal
 }  // namespace webrtc