CDM workarounds for OEMCrypto issues

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

libwvdrmengine/cdm/test/request_license_test.cpp

@@ -1043,7 +1043,8 @@ TEST_P(WvCdmUsageInfoTest, DISABLED_UsageInfo) {
     switch (status) {
       case KEY_MESSAGE: EXPECT_FALSE(usage_info.empty()); break;
       case NO_ERROR: EXPECT_TRUE(usage_info.empty()); break;
-      default: FAIL() << "GetUsageInfo failed with error " << status ; break;
+      default: FAIL() << "GetUsageInfo failed with error "
+                    << static_cast<int>(status) ; break;
     }
   }
 }
@@ -1258,15 +1259,9 @@ TEST_F(WvCdmRequestLicenseTest, SecurityLevelPathBackwardCompatibility) {
   TestWvCdmClientPropertySet property_set;
   property_set.set_security_level(QUERY_VALUE_SECURITY_LEVEL_L3);
 
-  EXPECT_EQ(NO_ERROR,
+  EXPECT_EQ(wvcdm::NEED_PROVISIONING,
             decryptor_.OpenSession(g_key_system, &property_set, &session_id_));
 
-  wvcdm::CdmAppParameterMap app_parameters;
-  std::string server_url;
-  EXPECT_EQ(wvcdm::NEED_PROVISIONING,
-            decryptor_.GenerateKeyRequest(
-                session_id_, key_set_id, "video/mp4", key_id,
-                kLicenseTypeStreaming, app_parameters, &key_msg_, &server_url));
   EXPECT_EQ(NO_ERROR, decryptor_.GetProvisioningRequest(
                           cert_type, cert_authority, &key_msg_,
                           &provisioning_server_url));