[ Merge of http://go/wvgerrit/16241 and http://go/wvgerrit/16364 ]
This will allow a usage session to be loaded later by key set ID.
This is needed for EME-style secure stop in the new CE CDM API.
b/25816911
Change-Id: I916340047492fbc0556d0e90bd2eac0f3eafe597