code: function() {
  			if (this._dropdownTriggerButton) {
  				if (this._dropdownTriggerButton.dropdown) {
  					this._dropdownTriggerButton.dropdown.destroy();
  					this._dropdownTriggerButton.dropdown = null;
  				}
  				this._dropdownTriggerButton = null;
  			}
  		}
docs: Destroys this dropdown and cleans up its resources.