Only pass whole clear frames to OEMCrypto_CopyBuffer

[ Merge from http://go/wvgerrit/16499 ]

Passing clear subsamples to OEMCrypto_CopyBuffer and encrypted subsamples
to OEMCrypto_DecryptCTR was causing performance issues as a lack of crypto
session information made it hard to associate clear and encrypted
subsamples with each other.

[ Based on a patch from Kelly Ren/Qualcomm ]

b/26538744

Change-Id: I4644f197b2ec481f6aa89d3fce29b22ebb7b0c06

libwvdrmengine/cdm/core/src/crypto_session.cpp

@@ -669,7 +669,9 @@ CdmResponseType CryptoSession::Decrypt(const CdmDecryptionParameters& params) {
   }
 
   OEMCryptoResult sts = OEMCrypto_ERROR_NOT_IMPLEMENTED;
-  if (!params.is_encrypted) {
+  if (!params.is_encrypted  &&
+      params.subsample_flags ==
+          (OEMCrypto_FirstSubsample | OEMCrypto_LastSubsample)) {
     sts = OEMCrypto_CopyBuffer(requested_security_level_,
                                params.encrypt_buffer, params.encrypt_length,
                                &buffer_descriptor, params.subsample_flags);