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

webrtc/pc/rtcstats_integrationtest.cc

Index: webrtc/pc/rtcstats_integrationtest.cc
diff --git a/webrtc/pc/rtcstats_integrationtest.cc b/webrtc/pc/rtcstats_integrationtest.cc
index 3337c4ee8b4944e41646780acb0c427bd1a61544..7d776d97adbd7f09728748cd206259fecf06ba08 100644
--- a/webrtc/pc/rtcstats_integrationtest.cc
+++ b/webrtc/pc/rtcstats_integrationtest.cc
@@ -475,6 +475,8 @@ class RTCStatsReportVerifier {
       verifier.TestMemberIsUndefined(media_stream_track.echo_return_loss);
       verifier.TestMemberIsUndefined(
           media_stream_track.echo_return_loss_enhancement);
+      verifier.TestMemberIsUndefined(media_stream_track.total_audio_energy);
+      verifier.TestMemberIsUndefined(media_stream_track.total_samples_duration);
     } else {
       RTC_DCHECK_EQ(*media_stream_track.kind,
                     RTCMediaStreamTrackKind::kAudio);
@@ -491,6 +493,12 @@ class RTCStatsReportVerifier {
       verifier.TestMemberIsUndefined(media_stream_track.full_frames_lost);
       // Audio-only members
       verifier.TestMemberIsNonNegative<double>(media_stream_track.audio_level);
+      // Audio tracks are expected to have audio energy/duration values that can
+      // be used to compute audio levels between getStats calls.

[hbos, 2017/07/07 12:52:24]

nit: I think this comment is superfluous, we don't have them for all the other
TestMember...

[Taylor Brandstetter, 2017/07/07 16:15:15]

Yeah, may be now. I think I added it before because it was a special case (only
worked for remote tracks).

[Zach Stein, 2017/07/07 21:27:37]

Agreed.

+      verifier.TestMemberIsNonNegative<double>(
+          media_stream_track.total_audio_energy);
+      verifier.TestMemberIsNonNegative<double>(
+          media_stream_track.total_samples_duration);
       // TODO(hbos): |echo_return_loss| and |echo_return_loss_enhancement| are
       // flaky on msan bot (sometimes defined, sometimes undefined). Should the
       // test run until available or is there a way to have it always be