Populate "total_round_trip_time" and "round_trip_time_measurements" for remote inbound RTP streams

Spec: https://w3c.github.io/webrtc-stats/#remoteinboundrtpstats-dict*

Adding them into the stats definition as well.

Bug: webrtc:12507
Change-Id: Id467a33fe7bb256655b68819e3ce87ca9af5b25f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/209000
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33363}
diff --git a/api/stats/rtcstats_objects.h b/api/stats/rtcstats_objects.h
index f328326..46bc018 100644
--- a/api/stats/rtcstats_objects.h
+++ b/api/stats/rtcstats_objects.h
@@ -556,6 +556,8 @@
   RTCStatsMember<std::string> local_id;
   RTCStatsMember<double> round_trip_time;
   RTCStatsMember<double> fraction_lost;
+  RTCStatsMember<double> total_round_trip_time;
+  RTCStatsMember<int32_t> round_trip_time_measurements;
 };
 
 // https://w3c.github.io/webrtc-stats/#dom-rtcmediasourcestats