MSE-in-Workers and MediaSourceHandle transfer/usage semantics question

karlt <https://github.com/karlt> did some analysis [1] of some potential
interop/ergonomic ambiguities around what a conformant implementation of
the MSEIW srcObject refinements
<https://github.com/w3c/media-source/pull/306> would need to do when the
application attempts to transfer a *MediaSourceHandle* object that is
currently set on a *srcObject* attribute of an *HTMLMediaElement*.

In the April media WG call, there was not enough attendance to obtain a
good consensus on which direction might be preferred by implementors and
web authors.

I'll discuss this also in today's WG call, though please also provide any
input you might have on the question of which option in [1] (1-4, or some
new option you may propose) you believe would be most ergonomic and
compatible with existing idioms.

Thank you,
Matt

[1] https://github.com/w3c/media-source/pull/306#pullrequestreview-928290232