code: function(markName) {
  			if (window.performance && window.performance.mark !== undefined) {
  				window.performance.mark(markName);
  			}
  		}
docs: @member {Function} mark Shims creating a new named time stamp, called a mark
  @param {String} markName String name to record how long it took to get there.
  A mark that already exists will be overwritten.