am a912c194: Merge "some clean up of video size change notification" into lmp-dev

* commit 'a912c194':
  some clean up of video size change notification
  delay data source creation for GenericSource prepare time
  Revert "NuPlayer: don't feed decoder input data during flushing."
  some fixes for crash when extractor creation fails
  Revert GenericSource track selection changes
  GenericSource: start/stop tracks correctly on selection
  CameraService: Clean up availability listeners and HAL error codes
  StagefrightRecorder: check for WEBM format instead of MP4
  stagefright: handle seeking to before first cue-point.