AbstractReadonlykindOptionalsidindicates current state of stream, it'll indicate paused if the track
has been paused by congestion controller
current receive bits per second
Abstractiscreates a new HTMLAudioElement or HTMLVideoElement, attaches to it, and returns it
attaches track to an existing HTMLAudioElement or HTMLVideoElement
Abstractstart
sid is set after track is published to server, or if it's a remote track