Bug 1318971 - Update !MOZ_WEBSPEECH case in ContentParent::RecvPSpeechSynthesisConstructor to return mozilla::ipc::IPCResult. r=kanru

dom/ipc/ContentParent.cpp

@@ -3144,7 +3144,7 @@ ContentParent::RecvPSpeechSynthesisConstructor(PSpeechSynthesisParent* aActor)
 #ifdef MOZ_WEBSPEECH
   return IPC_OK();
 #else
-  return false;
+  return IPC_FAIL_NO_REASON(this);
 #endif
 }