WPT details: Yes. Some tests exist in the current WebRTC WPT test suite, but additional tests will be added as part of the development of the feature.
Allows changing the association between the track associated with an RTCRtpSender and streams. Stream association causes tracks in the same stream to be synchronized. This is useful, for example, if during a call a user switches from a front-facing camera to a back-facing camera and the application uses RTCRtpSender.replaceTrack(). On the receiving end the new track must be associated with the existing stream and synchronized with its auto track.