SDK / exoplayer

We verified there is a race condition in the
AsynchronousMediaCodecAdapter when flushing the adapter
multiple times. The race condition results in calling MediaCodec.start()
and MediaCodec.flush() in parallel and that makes the MediaCodec
raise an exception.

This changes the default behavior to call MediaCodec.start() on the
same thread after MediaCodec.flush() to avoid the race condition.

#minor-release

PiperOrigin-RevId: 410509388