k.length;  // strip outer.
          // <outer><inner></outer><!--X--></inner>
          return tagStackToHtml(
              stack,
              '<' + outer + '><' + inner + '>'
              + '</' + outer + '><!--X--></' + inner + '>');
        }
      }
      return null;
    }

    function check(outer, inner, body, result) {
      var innerEl = body.getElementsByTagName(inner)[0];
      var closers = getOwn(result, inner) || [];
      if (!elementContainsComment(innerEl)) {
        closers.push(outer