WPT details: Yes, a test case is included in the CL where this is implemented.
Add RTP timestamp to RTCRtpReceiver.RTCRtpContributingSource. This is additional metadata to the existing RTP source.
This is needed to make it possible to link the information in RTCRtpContributingSource to a specific video/audio frame. One use case is a server-client WebRTC system where the client can now synchronize external events to a particular source frame and send this information back to the server.
Docs: https://w3c.github.io/webrtc-pc/#dom-rtcrtpcontributingsource
Explainers: https://github.com/w3c/webrtc-pc/issues/2177