class ViewsMenuLinkForm

class ViewsMenuLinkForm extends MenuLinkDefaultForm {
  
  /**
   * The edited views menu link.
   *
   * @var \Drupal\views\Plugin\Menu\ViewsMenuLink
   */
  protected $menuLink;
  
  /**
   * {@inheritdoc}
   */
  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
    // Put the title field first.
    $form['title'] = [
      '#type' => 'textfield',
      '#title' => $this->t('Title'),
      // @todo Ensure that the view is not loaded with a localized title.
      //   https://www.drupal.org/node/2309507
'#default_value' => $this->menuLink
        ->getTitle(),
      '#weight' => -10,
    ];
    $form['description'] = [
      '#type' => 'textfield',
      '#title' => $this->t('Description'),
      '#description' => $this->t('Shown when hovering over the menu link.'),
      // @todo Ensure that the view is not loaded with a localized description.
      //   https://www.drupal.org/node/2309507
'#default_value' => $this->menuLink
        ->getDescription(),
      '#weight' => -5,
    ];
    $form += parent::buildConfigurationForm($form, $form_state);
    $form['info']['#weight'] = -8;
    $form['path']['#weight'] = -7;
    $view = $this->menuLink
      ->loadView();
    $id = $view->storage
      ->id();
    $label = $view->storage
      ->label();
    if ($this->moduleHandler
      ->moduleExists('views_ui')) {
      $message = $this->t('This link is provided by the Views module. The path can be changed by editing the view <a href=":url">@label</a>', [
        ':url' => Url::fromRoute('entity.view.edit_form', [
          'view' => $id,
        ])->toString(),
        '@label' => $label,
      ]);
    }
    else {
      $message = $this->t('This link is provided by the Views module from view %label.', [
        '%label' => $label,
      ]);
    }
    $form['info']['#title'] = $message;
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function extractFormValues(array &$form, FormStateInterface $form_state) {
    $definition = parent::extractFormValues($form, $form_state);
    $definition['title'] = $form_state->getValue('title');
    $definition['description'] = $form_state->getValue('description');
    return $definition;
  }

}