- Bring back requirement for the first video frame to be rendered
before isReady returns true, *unless* we've deduced that the
upstream source is serving multiple renderers.
- Ditto for requiring that the audio track has some buffered data.
- cache ref didn't work because it referred to a private variable
(which isn't documented) from a public interface definition
(which is). Meaning the Javadoc generator was trying to link
to documentation that didn't exist.
- Make MediaCodecTrackRenderer.isReady more permissive.
This largely fixes#21
- Bring WebmExtractor closer to FragmentedMp4Extractor.
The two will probably be placed under a common interface
fairly soon, which will allow significant code
deduplication.
AudioTrack time will go out of sync if the decodeOnly flag
is set of arbitrary samples (as opposed to just those following
a seek). It's a pretty obscure case and it would be weird for
anyone to do it, but we should be robust against it anyway.