The spec is light in terms of how enabled=false tracks should be handled by HTMLMediaElement.

There are a few behavioural changes that are worth tightening:

1. Should rvfc callbacks be called for each frame of an enabled=false tracks?
   From testing, it appear rvfc callbacks are called for both Chrome and Safari. It seems though that if all tracks are enabled=false, UA may stop camera and callbacks would no longer be called. It might be more deterministic if rvfc is never called for an enabled=false track.
2. Should change of video frame size alter the media element size? Chrome, Safari and Firefox seem to update the size.
3. What should videoWidth/videoHeight return? Chrome and Safari seem to return the latest frame size, Firefox returns 1.