Add totalDecodeTime to RTCInboundRTPStreamStats

Pull request to WebRTC stats specification:
https://github.com/w3c/webrtc-stats/pull/450

Bug: webrtc:10775
Change-Id: Id032cb324724329fee284ebc84595b9c39208ab8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/144035
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28440}
diff --git a/pc/rtc_stats_collector.cc b/pc/rtc_stats_collector.cc
index fb85092..ec917ae 100644
--- a/pc/rtc_stats_collector.cc
+++ b/pc/rtc_stats_collector.cc
@@ -312,6 +312,9 @@
   inbound_video->key_frames_decoded = video_receiver_info.key_frames_decoded;
   if (video_receiver_info.qp_sum)
     inbound_video->qp_sum = *video_receiver_info.qp_sum;
+  inbound_video->total_decode_time =
+      static_cast<double>(video_receiver_info.total_decode_time_ms) /
+      rtc::kNumMillisecsPerSec;
   if (video_receiver_info.last_packet_received_timestamp_ms) {
     inbound_video->last_packet_received_timestamp =
         static_cast<double>(