At STARTED_AS_NEXT, offload MediaPlayer.start() to a separate thread

Fixes: 65210445
Fixes: 64915666
Test: adb shell am instrument -e size small -w 'android.media.cts/android.support.test.runner.AndroidJUnitRunner'
Change-Id: I73f1cebdd4b990e28f8d466f129e781cba2b5bbf
1 file changed