I added a few error codes for out-of-resource type conditions.
I added comments explain which functions may be called simultaneously.
Basically, info only functions, like getDeviceId, may be called anytime after
initialization. Functions that have a session parameter may be called at the
same time as other functions for a different session, but not for the same session.
Functions that create or delete sessions may not be called as the same time as any
each other, or at the same time as any session functions. The CDM is required to
honor these conventions.
If the OEM can only decrypt for one session at a time, it is the OEM's
responsibility to hold a lock.
Change-Id: If4b11afd70b5b2e67d78802ea0057fb25271ae90
d5aa1e41d3