code: function jscoverage_tabIndexOf(tab) {
    if (typeof tab === 'string') {
      tab = document.getElementById(tab);
    }
    var tabs = document.getElementById('tabs');
    var i;
    var child;
    var tabNum = 0;
    for (i = 0; i < tabs.childNodes.length; i++) {
      child = tabs.childNodes.item(i);
      if (child.nodeType === 1) {
        if (child === tab) {
          return tabNum;
        }
        tabNum++;
      }
    }
  //#JSCOVERAGE_IF 0
    throw "Tab not found";
  //#JSCOVERAGE_ENDIF
  }
docs: Returns an integer (0, 1, 2, or 3) representing the index of a given tab.
  @param  tab  the ID of the tab element
  OR
  the tab element itself