setBackCallback(callback, context, parameters) {
    if (callback == null) {
      this.resetBackCallback();
    } else {
      this._backCallback = callback;
      this._backContext = context;
      this._backParameters = parameters;
    }
  }
Sets a callback to fire when back occurs.
@param {Function} callback
@param {*} [context=this]
@param {Array} [parameters=null]