public IEnumerator <GeckoNode> GetEnumerator()
        {
            var xpathResult = new XPathResult((mozIDOMWindowProxy)_window, (nsISupports)_xpathResult.Object);

            while (!xpathResult.InvalidIteratorState)
            {
                var result = xpathResult.IterateNext().Wrap(_window, GeckoNode.Create);
                if (result == null)
                {
                    yield break;
                }
                yield return(result);
            }
        }