code: function addDynamicCssRule(uniqueToken, site, selector, body) {
          flushDynamicCssRules();
          var rule = "." + _Constants._listViewClass + " ." + uniqueToken + " " + selector + " { " +
               body +
          "}";
          var perfId = "_addDynamicCssRule:" + uniqueToken + ",info";
          if (site) {
              site._writeProfilerMark(perfId);
          } else {
              _WriteProfilerMark("WinJS.UI.ListView:Layout" + perfId);
          }
          layoutStyleElem.sheet.insertRule(rule, 0);
      }
docs: Creates a dynamic CSS rule and adds it to the DOM. uniqueToken is a class name which uniquely identifies a set of related rules. These rules may be removed using deleteDynamicCssRule. uniqueToken should be created using uniqueCssClassName.