This is exposing something that is already exposed in the legacy getStats() API and is only available if the "video-timing" header extension is used. Adding this metric here should unblock legacy getStats() API deprecation. The follow-up to unship or standardize this metric is tracked by https://crbug.com/webrtc/14586. Bug: webrtc:14587 Change-Id: Ic3d45b0558d7caf4be2856a4cd95b88db312f85e Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/279860 Reviewed-by: Harald Alvestrand <hta@webrtc.org> Commit-Queue: Henrik Boström <hbos@webrtc.org> Cr-Commit-Position: refs/heads/main@{#38444}