The allocator and buffering policy (e.g. how large the buffer
is) is moving to the top level as part of playlist support,
so it no longer makes sense to inject these parameters as
args into ExtractorSampleSource's constructor.
Instantiating the allocator and buffer size inside of the
source is temporary and only until they're moved up.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=123968976
DemoPlayer moves into core library as SimpleExoPlayer, which
implements ExoPlayer.
Issue: #383
Issue: #592
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=123090184
Allows the user to provide their own criteria for selecting one of the available tracks
without having to reimplement the track assignment logic, i.e. linking type x tracks with
type x renderer.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=122422087
prepare(SampleSource) is renamed to setSource(SampleSource). The player
immediately transitions to STATE_BUFFERING when the source is set, at which
point doSomeWork is called.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=119838825
