Merge of https://widevine-internal-review.googlesource.com/#/c/10614/
from the widevine cdm repo.
* b/15467844 - GenerateRSASignature returns OEMCrypto_ERROR_INVALID_CONTEXT
when called with a non-NULL signature pointer and signature length of
0 (rather than OEMCrypto_ERROR_SHORT_BUFFER)
* b/15989260 - OEMCrypto_DecryptCTR does not return OEMCrypto_ERROR_KEY_EXPIRED
after keys have expired
Also addresses
* integration test updated to reflect that loading certificate errors are
returned on OpenSession rather than GenerateKeyRequest
* compiler warning on type casting
b/15989261
Change-Id: Ib68b972651479e99b9d05de4493aac55a96c4f39
2ec3049bda