Gonk media code should be the only place where this is still used. Marking as deprecated for now, and I will remove it at a future point in time as part of a planned cleanup of unused media code.
This was originally added to make MediaPromise dispatch reliable in the
presence of the Flush() feature of MediaTaskQueue. That feature has
now been restricted to a special subclass (which we should eventually eliminate),
so we can just assert that MediaPromises are never used on those task queues
and simplify the rest of the code.
trav90
Moonchild