Adding stats that can be used to compute output audio levels.

webrtc/pc/rtcstatscollector.cc

Index: webrtc/pc/rtcstatscollector.cc
diff --git a/webrtc/pc/rtcstatscollector.cc b/webrtc/pc/rtcstatscollector.cc
index ca995327d5f21d19623e36c290c5a2941f1df431..949f0429aada9238cc9d9eab4ea899a987553b46 100644
--- a/webrtc/pc/rtcstatscollector.cc
+++ b/webrtc/pc/rtcstatscollector.cc
@@ -405,6 +405,10 @@ ProduceMediaStreamTrackStatsFromVoiceReceiverInfo(
     audio_track_stats->audio_level = DoubleAudioLevelFromIntAudioLevel(
         voice_receiver_info.audio_level);
   }
+  audio_track_stats->total_audio_energy =
+      voice_receiver_info.total_output_energy;
+  audio_track_stats->total_samples_duration =
+      voice_receiver_info.total_output_duration;
   return audio_track_stats;
 }