*aResult = mResult;
NS_ADDREF(*aResult = mResult);
ContainerEnumeratorImpl::GetNext(nsISupports** aResult){    nsresult rv;    PRBool hasMore;    rv = HasMoreElements(&hasMore);    if (NS_FAILED(rv)) return rv;    if (! hasMore)        return NS_ERROR_UNEXPECTED;    // Don't AddRef: we "transfer" ownership to the caller    *aResult = mResult;    mResult = nsnull;    return NS_OK;}