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/media/base/media_channel.h b/media/base/media_channel.h
index 8a97022..80a7e11 100644
--- a/media/base/media_channel.h
+++ b/media/base/media_channel.h
@@ -601,6 +601,8 @@
   uint32_t key_frames_decoded = 0;
   uint32_t frames_rendered = 0;
   absl::optional<uint64_t> qp_sum;
+  // https://w3c.github.io/webrtc-stats/#dom-rtcinboundrtpstreamstats-totaldecodetime
+  uint64_t total_decode_time_ms = 0;
   int64_t interframe_delay_max_ms = -1;
   uint32_t freeze_count = 0;
   uint32_t pause_count = 0;