Merge from Widevine repo of http://go/wvgerrit/55461
This CL allows provisioning 3.0 devices to install their OEM certs
from an initialization partition. This method is already used for
keyboxes on Android -- we are just adding the ability to use it for
OEM certs, also.
Also, for v15, we require OEMCrypto to report a valid certificate in
the unit tests.
bug: 111725154
test: unit tests
Change-Id: I142c84a1a67bdb4cee943cfd12a632421901eb24
562c14b5f1