Add |legacy_destination_url| back to SessionMessage for EME

ppapi/cpp/private/content_decryptor_private.h

Index: ppapi/cpp/private/content_decryptor_private.h
diff --git a/ppapi/cpp/private/content_decryptor_private.h b/ppapi/cpp/private/content_decryptor_private.h
index 0117c72dfa3332243805bf1790b938cd817e6299..589c3a7b3e5689314b67263ae1608c7a36da804b 100644
--- a/ppapi/cpp/private/content_decryptor_private.h
+++ b/ppapi/cpp/private/content_decryptor_private.h
@@ -81,7 +81,8 @@ class ContentDecryptor_Private {
                        const std::string& error_description);
   void SessionMessage(const std::string& web_session_id,
                       PP_CdmMessageType message_type,
-                      pp::VarArrayBuffer message);
+                      pp::VarArrayBuffer message,
+                      const std::string& legacy_destination_url);
   void SessionKeysChange(const std::string& web_session_id,
                          bool has_additional_usable_key,
                          const std::vector<PP_KeyInformation>& key_information);