Add stats totalSamplesReceived and concealedSamples

Adds two new stats to RTCMediaStreamTrackStats:
* totalSamplesReceived is the total number of samples received on
      the audio channel and includes real and synthetic samples.
* concealedSamples is the total number of synthetic samples
      received on the audio channel used to conceal packet loss.

Bug: webrtc:8076
Change-Id: I36e9828525ec341490cf3310a972b56a8b443667
Reviewed-on: https://chromium-review.googlesource.com/615902
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19506}
diff --git a/webrtc/api/stats/rtcstats_objects.h b/webrtc/api/stats/rtcstats_objects.h
index 071a7fb..0cbea7c 100644
--- a/webrtc/api/stats/rtcstats_objects.h
+++ b/webrtc/api/stats/rtcstats_objects.h
@@ -273,9 +273,11 @@
   // Audio-only members
   RTCStatsMember<double> audio_level;
   RTCStatsMember<double> total_audio_energy;
-  RTCStatsMember<double> total_samples_duration;
   RTCStatsMember<double> echo_return_loss;
   RTCStatsMember<double> echo_return_loss_enhancement;
+  RTCStatsMember<uint64_t> total_samples_received;
+  RTCStatsMember<double> total_samples_duration;
+  RTCStatsMember<uint64_t> concealed_samples;
 };
 
 // https://w3c.github.io/webrtc-stats/#pcstats-dict*