onMenuKeydown(e) {
    const el = /** @type {?HTMLElement} */ (e.target);

    switch (e.code) {
      case 'ArrowUp':
        e.preventDefault();
        this._getPreviousMenuItem(el).focus();
        break;
      case 'ArrowDown':
        e.preventDefault();
        this._getNextMenuItem(el).focus();
        break;
      case 'Home':
        e.preventDefault();
        this._getNextMenuItem().focus();
        break;
      case 'End':
        e.preventDefault();
        this._getPreviousMenuItem().focus();
        break;
      default:
       // no op
    }
  }
Handler for tool DropDown.
@param {KeyboardEvent} e