SDK / exoplayer

Issue #641

1. [Cleanup] Remove unused Track types, including TYPE_TIME_CODE.
2. Add subtitle track type, which is different to the existing text type.
3. Set duration on the media formats for text and subtitle tracks. This
   was causing the player to report unknown media duration for mp4 files
   containing such tracks.
4. Make TextTrackRenderer do the right thing when not started.

Issue: #635

- Make UnrecognizedInputFormatException public so the app can more easily handle
  it when it is propagated to onPlayerError.
- Format the description using the simple class names for the extractors.
- Don't retry loading after it's thrown, but just throw immediately.

Issue: #641

Add support for HEVC video in Matroska files

add support s263

- ExtractorSampleSource takes an array of extractors to test for suitability.
- Extractors now implement a sniff() method that returns whether they can
  extract samples in the input stream's format.
- Switch demo app samples to use format detection.

Issue: #438

Issue: #599

1. Fix seeking in test2.mkv by handling non-default timescale
   after duration.
2. Fix handling of missing cues in test6.mkv by allowing playback
   to continue (but all seeks will reset to t=0).

Issue #631

Issue: #595

GitHub issue: #589

Issue: #589

The ID_SEGMENT can only be read once, as seeing the element a second time is
assumed to indicate that the file contains multiple segment elements (which is
not supported).

This change allows the element to be read twice if it is at the same position,
so that retrying loading from the start can succeed.

This ensures FLAG_END_OF_STREAM doesn't get permanently stuck.

1. Workaround for decoders that fail to handle the END_OF_STREAM flag.
2. Revert processing of final output buffer if it's non-empty. This
   introduced another bug (#596)

Reverts: b88012f5
Issue: #417
Issue: #596