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
    }
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