This aligns the method naming and Javadoc. The only remaining
inconsistency I can see is that the initial reference count for
DrmSession is 0 rather than 1. Unfortunately I think it's not
trivial to get these aligned, because DefaultDrmSessionManager
relies on being able to do something between instantiation and
the DrmSession starting to open the session. In practice this
doesn't really matter, since DrmSessions will be obtained via the
manager, which does increment thee reference count to 1 to be
consistent with how ExoMediaDrm acquisition works.
PiperOrigin-RevId: 280136574
7ca77c6002