Ok, it looks functional but there's no back-compatibility for old ParserCache renderings of pages containing media items.
This could probably be worked around by always loading a tiny stub module that checks at content-insertion / load time for the presence of transformable media and then loads the other modules needed to trigger the transform. This would might increase the FOUC effect on those pages, but they would continue to work...
If we were ready to go on VideoJS I'd say don't bother fixing this, but we're going to need some more time to swap out the player frontend properly... I think it makes sense to give just enough proper infrastructure for TMH's MwEmbedPlayer that we can make it hot-swappable via a Beta Features option, and this is a necessary step along that way.
That'll let us work on the new VideoJS stuff for early adopters and testers while limping along with existing MwEmbedPlayer with minimal breakage...
-- brion