SDK / exoplayer

support content uri (e.q. content://xxx)

Support setting properties on MediaDrm

Gradle plugin 1.2.3

When a passthrough AudioTrack is replaced (due to seeking) the new one behaves
as if it is still emptying data from the old one, with its playback position
advancing until it runs out of data.

Data written while the 'old' AudioTrack was emptying would be discarded, so
avoid writing to the new AudioTrack while the old one is still emptying.

Also avoid using AudioTrack.getTimestamp with passthrough tracks, as this causes
the playback position to jump to a position that breaks audio/video
synchronization.

This also fixes a technical mistake where HlsChunkSource is fed
seekPositionUs=-1 when obtaining the first chunk. This is wrong,
but the usage of this variable within HlsChunkSource enforces that
the seek must stay within bounds, so we get away with it.

Issue: #385

Issue: #400

1. prepare() needs to load a TsChunk to actually prepare the source.
2. Source is prepared, but no tracks are enabled (this is why it's
   an edge case - no-one is likely to be doing this!).
3. The TsChunk load completes.

We should not load additional chunks in this case.

Simple gradle updates

Partly fixes #434 as the AC-3 stream will now be ignored if the
audio capabilities don't allow it to be played back.

Issue #434

Issue: #423

Issue: #407