os->AddObserver(result, NS_MEMORY_PRESSURE_TOPIC);
os->AddObserver(result, NS_MEMORY_PRESSURE_TOPIC, PR_TRUE);
NS_NewXBLService(nsIXBLService** aResult){  nsXBLService* result = new nsXBLService;  if (! result)    return NS_ERROR_OUT_OF_MEMORY;  NS_ADDREF(*aResult = result);  // Register the first (and only) nsXBLService as a memory pressure observer  // so it can flush the LRU list in low-memory situations.  nsCOMPtr<nsIObserverService> os = do_GetService(NS_OBSERVERSERVICE_CONTRACTID);  if (os)    os->AddObserver(result, NS_MEMORY_PRESSURE_TOPIC);  return NS_OK;}