Fix and improve handling of audio session IDs

[master255]

@ojw28 Perhaps you need to pay special attention to AudiosessionId, and to test its work properly?
I regularly come across the fact that it does not work:
#6954.
#6975

ExoPlayer 2.12.0
Android 4.4 audio session stops transmitting data after rewinding and when you switch to the next track. There are no errors or notifications in the logs.

mMediaPlayer.getAudioSessionId() - method does not work. It regularly returns 0 at the time when the session number is different.

[ojw28]

If you want us to investigate this, please provide proper reproduction steps, ideally in the form of a minimal test app. Note that #6954 also lacked clear reproduction steps, to the extent that it's still unclear whether there was a bug. #6975 also lacked clear reproduction steps until 12 messages in, and when they were finally provided we were able to provide a clear answer.

[google-oss-bot]

Hey @master255. We need more information to resolve this issue but there hasn't been an update in 14 weekdays. I'm marking the issue as stale and if there are no new updates in the next 7 days I will close it automatically.

If you have more information that will help us get to the bottom of this, just add a comment!

[master255]

@google-oss-bot This is your module. You should test it, not me. If you are not interested, I can do nothing to help.
I switched to VLC. It has a better sound and a better picture.