Pushed by pehrsons@gmail.com: https://hg.mozilla.org/integration/autoland/rev/109d1020117a In WPT test that a peer connection receiving video cannot be garbage collected. r=jib https://hg.mozilla.org/integration/autoland/rev/c28bf2b7d094 Move RemoteTrackSource definitions to cpp file. r=bwc https://hg.mozilla.org/integration/autoland/rev/0f2aa0156add Implement reference traversal and unlinking for RemoteTrackSource. r=bwc https://hg.mozilla.org/integration/autoland/rev/4efc6b3c9527 Consolidate PeerConnectionImpl's PrivacyRequested and PrivacyNeeded. r=bwc https://hg.mozilla.org/integration/autoland/rev/dea5d02d4dbb Use an enum for principal privacy in PeerConnectionImpl and friends. r=bwc https://hg.mozilla.org/integration/autoland/rev/a0d17c5a5b11 Trigger setting the private PrincipalHandle in MediaPipeline through RTCRtpReceiver. r=bwc https://hg.mozilla.org/integration/autoland/rev/f2d5a8a91ed2 Make RemoteTrackSource an RTCRtpReceiver member and add it to CC traversal. r=bwc https://hg.mozilla.org/integration/autoland/rev/61a7f60b178c Simplify remote SourceMediaTrack ownership model. r=bwc https://hg.mozilla.org/integration/autoland/rev/be83a372e63b Move unmute-after-enabling logic out of MediaPipeline into RTCRtpReceiver. r=bwc https://hg.mozilla.org/integration/autoland/rev/765bd8c21710 Remove RemoteTrackSource from MediaPipeline. r=bwc https://hg.mozilla.org/integration/autoland/rev/5a551138a5d1 Fix some warnings around MediaPipeline. r=bwc https://hg.mozilla.org/integration/autoland/rev/d1dbd2ad49ba In RemoteTrackSource add a ref to RTCRtpReceiver to prevent GC at the wrong time. r=bwc https://hg.mozilla.org/integration/autoland/rev/f3f3da28953c Rename ConcreteConduitControl to not be specific for conduits. r=bwc https://hg.mozilla.org/integration/autoland/rev/677062c9bf1a Rework RTCRtpReceiver unmute logic through Watchables. r=bwc https://hg.mozilla.org/integration/autoland/rev/1c1098e1e1fc Signal start and stop to MediaPipeline through state mirroring. r=bwc https://hg.mozilla.org/integration/autoland/rev/1d8a6c3290a6 Remove unused member function declarations in RTCRtpSender.h. r=bwc https://hg.mozilla.org/integration/autoland/rev/3cf25f108bff In RTCRtpSender stop RTCDTMFSender playout through a WatchManager. r=bwc https://hg.mozilla.org/integration/autoland/rev/ebfb7a062761 Don't block unmute when the jseptrack is inactive. r=bwc

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/38433 for changes under testing/web-platform/tests

Upstream PR merged by moz-wptsync-bot