Per w3c/webrtc-pc#2220.

This solves the BUNDLE footgun, and in the process deprecates the JS-observable tc.stopped transceiver property in favor of a new "stopped" enum value in tc.direction and tc.currentDirection.

Firefox will likely continue to expose the stopped property for a release or two for backwards compatibility until we have telemetry numbers for it that justify deprecating it.

This is largely updated already in documentation, but there is some review to do, and IIRC I held off pulling the trigger on a few bits until it actually hit the spec proper. We may need to review some examples throughout content to change this.

On a related note, but not part of this work: we should review our documentation to start shifting some of it from using addTrack() to working with transceivers directly, as this is the new hotness.

Bugbug thinks this bug is a enhancement, but please change it back in case of error.

Byron and I agreed it makes sense to tackle https://github.com/w3c/webrtc-pc/pull/2160/files as well, as part of this work. That is: remove stopped transceivers from pc.getTransceivers() in SRD(offer).

Docs team: will not ship in 70.

Safari does not implement this yet. We have other web-compat bugs that are more of a parity problem than this right now.

Marking this as dependent on bug 1813468, since it is cleaning up a lot of the same code.

https://treeherder.mozilla.org/jobs?repo=try&revision=faec8b8e51453bd17063ec0b4adc20296cb28afd
https://treeherder.mozilla.org/jobs?repo=try&revision=7adaab19709592226c677575dcb5609f18677acd

Depends on D175260

https://treeherder.mozilla.org/jobs?repo=try&revision=f0388e33365482fd70fd6330397eff1d1cc4537e
https://treeherder.mozilla.org/jobs?repo=try&revision=89ef8924381d8008d2d1b1a390a4c0e46e0bcc3c
https://treeherder.mozilla.org/jobs?repo=try&revision=6d09276acf2bfbe04b699941706f9cc881f7e7cd

mochitest/crashtest/gtest look fine. Pathless wpt try push to work around bug 1830520:

https://treeherder.mozilla.org/jobs?repo=try&revision=a8e26a1abfe1ed1e98634baf9d834a812a7d9f4c

https://treeherder.mozilla.org/jobs?repo=try&revision=49643cddb606ce4a2655325185688275b8f618ed
https://treeherder.mozilla.org/jobs?repo=try&revision=9e8fd4945b9ddceb3d021f9f7aa8ec783d7fe1eb
https://treeherder.mozilla.org/jobs?repo=try&revision=a6afc9ce3cde99b3a9078d2c71a3df31e889edff

Try looks fine.

https://hg.mozilla.org/mozilla-central/rev/c1679789476d
https://hg.mozilla.org/mozilla-central/rev/b5bb91755232
https://hg.mozilla.org/mozilla-central/rev/39c307008548