There are multiple issues with HlsSampleSource's use of
LoadControl that become apparent when you attempt to use
the same LoadControl for loads by another source.
* In the "limbo" state HlsSampleSource doesn't start any
new loads, but doesn't update the LoadControl to tell
it that it doesn't want to load anything either. This
can prevent another source from starting the loads that
it needs to make to complete preparation, causing
playback to become stuck.
* The LoadControl isn't updated properly when the EOS is
reached. This can cause playback to become stuck near
the end of the media.
* If HlsSampleSource is released from being in the "limbo"
state, it doesn't unregister itself with the control.
Issue: #151
Issue: #676
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=111942009
2a9eeaa893