Merge from Widevine repo of http://go/wvgerrit/16499
With the increasing number of devices that support multiple screens or
windows, it is desireable to verify that OEMCrypto can have several
sessions open and actively decrypting at the same time.
Calls to OEMCrypto are still serialized -- this is not a threading
test -- but we still have multiple sessions open and decrypt from each
of them.
Change-Id: I5b24f4a464ed05a5b21625c66fe7989644b67a5a
35a080a57d