ther an inner tag leads to an inner element inside it.
  // For example, to test whether an <a> tag nestes properly in a <td>, we
  // need to construct <table><tbody><tr><td><a>.
  //
  // Knowing what needs to be on the open element stack for <td> requires
  // knowing what needs to be on the open element stack for <tr>.
  function containmentStackMaker(canAppearIn) {
    var memoTable = newBlankObject();
    return function (elementName, opt_exclusions) {
      if (elementName == 'body') {
        // The