AudioTrack.setOffloadEndOfStream should be called after a track
has been buffered. Additionally, the AudioTrack must be playing.
It has been observed that for very short media (<1s), the AudioTrack
might not have started immediately after the read that buffered
the audio.
In such a situation, calling AudioTrack.setOffloadEndOfStream throws
and playback fails.
Avoid this failure by checking that the AudioTrack is playing before
calling setOffloadEndOfStream.
This means that very short gapless media will not be gapless, this was
deemed acceptable given that such very short media should be very rare
in offload.
PiperOrigin-RevId: 450431146
