code: function addListener(obj, eventName, target, method) {
    Ember.assert("You must pass at least an object and event name to Ember.addListener", !!obj && !!eventName);
  
    if (!method && 'function' === typeof target) {
      method = target;
      target = null;
    }
  
    var actionSet = actionSetFor(obj, eventName, target, true),
        methodGuid = guidFor(method);
  
    if (!actionSet[methodGuid]) {
      actionSet[methodGuid] = { target: target, method: method };
    }
  
    if ('function' === typeof obj.didAddListener) {
      obj.didAddListener(eventName, target, method);
    }
  }
docs: The sendEvent arguments > 2 are passed to an event listener.
  
  @memberOf Ember