How should sender.get/setParameters work on a stopped sender?

[jan-ivar]

Should it throw InvalidStateError like sender.replaceTrack or be a no-op/return last set value?

[aboba]

@jan-ivar How about this?

getParameters returns the last value set (even if pc is closed??)

setParameters rejects the promise with InvalidStateError if transceiver.stopped is true.

Other cases:
If sender.track is null or the value of transceiver.currentDirection is recvonly, the sender will not send, but I'd suggest this not cause the promise to be rejected.

[alvestrand]

Since getParameters doesn't need to be special-cased, and pc.stop() stops all transceivers, the merge of #966 seems to resolve this issue.