RTCMediaStreamTrackStats.framesReceived collected by RTCStatsCollector.

VideoReceiverInfo::frames_received added based on
VideoReceiveStream::Stats::frame_counts (.key_frames + .delta_frames).

BUG=webrtc:6757, chromium:659137, chromium:627816

Review-Url: https://codereview.webrtc.org/2607913002
Cr-Original-Commit-Position: refs/heads/master@{#16185}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 42f6d2fb6ca224fc79cdb3cda9c2af886497fd6c
diff --git a/media/engine/webrtcvideoengine2.cc b/media/engine/webrtcvideoengine2.cc
index b0d3b89..da045ec 100644
--- a/media/engine/webrtcvideoengine2.cc
+++ b/media/engine/webrtcvideoengine2.cc
@@ -2383,6 +2383,8 @@
   info.jitter_buffer_ms = stats.jitter_buffer_ms;
   info.min_playout_delay_ms = stats.min_playout_delay_ms;
   info.render_delay_ms = stats.render_delay_ms;
+  info.frames_received = stats.frame_counts.key_frames +
+                         stats.frame_counts.delta_frames;
   info.frames_decoded = stats.frames_decoded;
 
   info.codec_name = GetCodecNameFromPayloadType(stats.current_payload_type);