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/statstypes.h b/webrtc/api/statstypes.h
index 57fe82d..819bfe0 100644
--- a/webrtc/api/statstypes.h
+++ b/webrtc/api/statstypes.h
@@ -104,6 +104,7 @@
     kStatsValueNameBytesReceived,
     kStatsValueNameBytesSent,
     kStatsValueNameCodecImplementationName,
+    kStatsValueNameConcealedSamples,
     kStatsValueNameDataChannelId,
     kStatsValueNameFramesDecoded,
     kStatsValueNameFramesEncoded,
@@ -120,6 +121,7 @@
     kStatsValueNameState,
     kStatsValueNameTotalAudioEnergy,
     kStatsValueNameTotalSamplesDuration,
+    kStatsValueNameTotalSamplesReceived,
     kStatsValueNameTransportId,
     kStatsValueNameSentPingRequestsTotal,
     kStatsValueNameSentPingRequestsBeforeFirstResponse,