function triggerWithArray(dispatcher, eventName, argsArray) {
        var triggerArgs = [eventName].concat(argsArray);
        dispatcher.trigger.apply(dispatcher, triggerArgs);
    }
Utility for calling on() with an array of arguments to pass to event handlers (rather than a varargs
list). makeEventDispatcher() must have previously been called on 'dispatcher'.
@param {!Object} dispatcher
@param {string} eventName
@param {!Array.<*>} argsArray