Add backward compatibility to OEMCrypto_CopyBuffer

Merge from Widevine repository of http://go/wvgerrit/13912

This CL falls back to OEMCrypto_DecryptCTR if the oemcrypto library
does not implement OEMCrypto_CopyBuffer.  This allows devices with
oem crypto version 9 to function as they previously did.

Change-Id: Id3a4a94b1fd559f426ee260cfbf7077fa9101d8b

libwvdrmengine/oemcrypto/mock/src/oemcrypto_mock.cpp

@@ -536,10 +536,11 @@ OEMCryptoResult SetDestination(OEMCrypto_DestBufferDesc* out_buffer,
           + out_buffer->buffer.secure.offset;
       *max_length =  out_buffer->buffer.secure.max_length;
       break;
-    default:
     case OEMCrypto_BufferType_Direct:
-      return OEMCrypto_ERROR_NOT_IMPLEMENTED;
+      *destination = NULL;
       break;
+    default:
+      return OEMCrypto_ERROR_INVALID_CONTEXT;
   }
 
   if (out_buffer->type != OEMCrypto_BufferType_Direct
@@ -616,7 +617,7 @@ OEMCryptoResult OEMCrypto_CopyBuffer(const uint8_t *data_addr,
                                        &max_length);
   if (sts != OEMCrypto_SUCCESS) return sts;
 
-  memcpy(destination, data_addr, data_length);
+  if (destination != NULL) memcpy(destination, data_addr, data_length);
   return OEMCrypto_SUCCESS;
 }