Reland "Piping audio interruption metrics to API layer"

The metrics are now added as RTCNonStandardStatsMember objects in
RTCMediaStreamTrackStats. Unit tests are updated.

This is a reland of https://webrtc-review.googlesource.com/c/src/+/134303,
with fixes.

TBR=kwiberg@webrtc.org

Bug: webrtc:10549
Change-Id: I29dcc6fbfc69156715664e71acfa054c1b2d9038
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/134500
Commit-Queue: Henrik Lundin <henrik.lundin@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Ivo Creusen <ivoc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27806}
diff --git a/api/stats/rtcstats_objects.h b/api/stats/rtcstats_objects.h
index 4ddfa93..96c7a03 100644
--- a/api/stats/rtcstats_objects.h
+++ b/api/stats/rtcstats_objects.h
@@ -321,6 +321,10 @@
   RTCNonStandardStatsMember<uint64_t> jitter_buffer_flushes;
   RTCNonStandardStatsMember<uint64_t> delayed_packet_outage_samples;
   RTCNonStandardStatsMember<double> relative_packet_arrival_delay;
+  // TODO(henrik.lundin): Add description of the interruption metrics at
+  // https://github.com/henbos/webrtc-provisional-stats/issues/17
+  RTCNonStandardStatsMember<uint32_t> interruption_count;
+  RTCNonStandardStatsMember<double> total_interruption_duration;
   // Non-standard video-only members.
   // https://henbos.github.io/webrtc-provisional-stats/#RTCVideoReceiverStats-dict*
   RTCNonStandardStatsMember<uint32_t> freeze_count;