code: function makeEventDispatcher(obj) {
          $.extend(obj, {
              on: on,
              off: off,
              one: one,
              trigger: trigger,
              _EventDispatcher: true
          });
          // Later, on() may add _eventHandlers: Object.<string, Array.<{event:string, namespace:?string,
          //   handler:!function(!{type:string, target:!Object}, ...)}>> - map from eventName to an array
          //   of handler records
          // Later, markDeprecated() may add _deprecatedEvents: Object.<string, string|boolean> - map from
          //   eventName to deprecation warning info
      }
docs: Adds the EventDispatcher APIs to the given object: on(), one(), off(), and trigger(). May also be
  called on a prototype object - each instance will still behave independently.
  @param {!Object} obj Object to add event-dispatch methods to