- scan internal tracks when necessary
- fix overflow in addTimedTextSource
- do not hide timed text track in doSelectDefaultTrack; i.e. apply
hiding logic to subtitle tracks only
- do not notify stop in scheduleUpdate; it will be fired in onStopped
if necessary
Bug: 17323221
Change-Id: I485f7d9197d10562fbd58d0afe5e9aa4cf610f1a