HTMLElement} b
       * @return {boolean}
       * @private
       */
      _hasLowerTabOrder: function(a, b) {
        // Normalize tabIndexes
        // e.g. in Firefox `<div contenteditable>` has `tabIndex = -1`
        var ati = Math.max(a.tabIndex, 0);
        var bti = Math.max(b.tabIndex, 0);
        return (ati === 0 || bti === 0) ? bti > ati : ati > bti;
      }
    };
  })();
</script>
