- MediaDrmEventListener.onEvent is typically called on the
app's main thread. mediaDrmHandler is instantiated on the
playback thread. Hence mediaDrmHandler should be volatile
to ensure visibility.
- Nulling mediaDrmHandler could result in a NPE in onEvent.
Instantiate mediaDrmHandler (and don't null it again) to
avoid this. MediaDrmHandler.handleMessage will correctly
discard any events for sessions that are now closed.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=168707938
