[mediacapture-fromelement] Tie MediaStreamTrack lifetime to the underlying AudioTrack or VideoTrack?

foolip has just created a new issue for 
https://github.com/w3c/mediacapture-fromelement:

== Tie MediaStreamTrack lifetime to the underlying AudioTrack or 
VideoTrack? ==
The spec for 
[`captureStream()`](http://w3c.github.io/mediacapture-fromelement/#widl-HTMLMediaElement-captureStream-MediaStream)
 says "Since a `MediaStreamTrack` can only end once, a track that is 
enabled, disabled and re-enabled will be captured as two separate 
tracks. Similarly, restarting playback after playback ends causes a 
new set of captured `MediaStreamTrack` instances to be created. 
Seeking during playback without changing track selection does not 
generate events or cause a captured `MediaStreamTrack` to end."

This seems like a complication, is it necessary? If a 
`MediaStreamTrack` has exactly the same lifetime as its corresponding 
`AudioTrack` or `VideoTrack`, one wouldn't have to re-create track 
when seeking after playback ends, and it would be a lot simpler to 
understand the model.

The price to pay is that a `MediaStreamTrack` would be producing 
nothing sometimes, but is that bad? It seems nice to at least pause on
 the last video frame without ending the MediaStreamTrack?

Please view or discuss this issue at 
https://github.com/w3c/mediacapture-fromelement/issues/24 using your 
GitHub account