code: function createEvent_(eventType, bubbles, cancelable) {
      if ('CustomEvent' in window && typeof window.CustomEvent === 'function') {
        return new CustomEvent(eventType, {
          bubbles: bubbles,
          cancelable: cancelable
        });
      } else {
        var ev = document.createEvent('Events');
        ev.initEvent(eventType, bubbles, cancelable);
        return ev;
      }
    }
docs: Create an event object.
  
  @param {string} eventType The type name of the event.
  @param {boolean} bubbles Whether the event should bubble up the DOM.
  @param {boolean} cancelable Whether the event can be canceled.
  @returns {!Event}