Useful functionality promoted to core library:
1. Management of SurfaceHolder.Callback lifecycle
promoted to SimpleExoPlayer
2. Ability to determine whether audio/video tracks
exist but are all unsupported promoted to
MappingTrackSelector.TrackInfo
3. Read external storage permissions check promoted
to Util
4. SubtitleView given ability to act directly as a
TextRenderer.Output to remove layer of indirection
5. SubtitleView given ability to configure itself to
user's platform wide caption styling
6. KeyCompatibleMediaController promoted to library's
UI package.
Relocation of boring stuff:
1. ID3 frame logging moved to EventLogger.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=128714230
