if (!it) return NS_ERROR_OUT_OF_MEMORY;
NS_ENSURE_TRUE(it, NS_ERROR_OUT_OF_MEMORY);
NS_NewXBLContentSink(nsIXMLContentSink** aResult,                     nsIDocument* aDoc,                     nsIURI* aURL,                     nsIWebShell* aWebShell){  NS_PRECONDITION(nsnull != aResult, "null ptr");  if (!aResult)    return NS_ERROR_NULL_POINTER;  nsXBLContentSink* it;  NS_NEWXPCOM(it, nsXBLContentSink);  if (!it)    return NS_ERROR_OUT_OF_MEMORY;  nsresult rv = it->Init(aDoc, aURL, aWebShell);  if (NS_FAILED(rv))    return rv;  return it->QueryInterface(NS_GET_IID(nsIXMLContentSink), (void **)aResult);}