Expose delayed packet outage as a cumulative metric of samples in the new getStats API.

The stat will be exposed through origin trial described in:
https://docs.google.com/document/d/1stYIZhEmDZ7NJF9gjjsM66eLFJUdc-14a3QutrFbIwI

Change-Id: Ib191a11c6bd9e617abbe9dd82239b0c5b4e6b4e0
Bug: webrtc:10043
Reviewed-on: https://webrtc-review.googlesource.com/c/111922
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Ivo Creusen <ivoc@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Reviewed-by: Minyue Li <minyue@webrtc.org>
Commit-Queue: Jakob Ivarsson‎ <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25802}
diff --git a/pc/rtcstatscollector.cc b/pc/rtcstatscollector.cc
index 33d4af1..d48ecc0 100644
--- a/pc/rtcstatscollector.cc
+++ b/pc/rtcstatscollector.cc
@@ -456,6 +456,8 @@
       voice_receiver_info.concealment_events;
   audio_track_stats->jitter_buffer_flushes =
       voice_receiver_info.jitter_buffer_flushes;
+  audio_track_stats->delayed_packet_outage_samples =
+      voice_receiver_info.delayed_packet_outage_samples;
   return audio_track_stats;
 }