class NodeRevisionRevertTranslationForm

class NodeRevisionRevertTranslationForm extends NodeRevisionRevertForm {

  /**
   * The language to be reverted.
   *
   * @var string
   */
  protected $langcode;

  /**
   * The language manager.
   *
   * @var \Drupal\Core\Language\LanguageManagerInterface
   */
  protected $languageManager;

  /**
   * Constructs a new NodeRevisionRevertTranslationForm.
   *
   * @param \Drupal\Core\Entity\EntityStorageInterface $node_storage
   *   The node storage.
   * @param \Drupal\Core\Datetime\DateFormatterInterface $date_formatter
   *   The date formatter service.
   * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
   *   The language manager.
   * @param \Drupal\Component\Datetime\TimeInterface $time
   *   The time service.
   */
  public function __construct(EntityStorageInterface $node_storage, DateFormatterInterface $date_formatter, LanguageManagerInterface $language_manager, TimeInterface $time) {
    parent::__construct($node_storage, $date_formatter, $time);
    $this->languageManager = $language_manager;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container
      ->get('entity_type.manager')
      ->getStorage('node'), $container
      ->get('date.formatter'), $container
      ->get('language_manager'), $container
      ->get('datetime.time'));
  }

  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'node_revision_revert_translation_confirm';
  }

  /**
   * {@inheritdoc}
   */
  public function getQuestion() {
    return $this
      ->t('Are you sure you want to revert @language translation to the revision from %revision-date?', [
      '@language' => $this->languageManager
        ->getLanguageName($this->langcode),
      '%revision-date' => $this->dateFormatter
        ->format($this->revision
        ->getRevisionCreationTime()),
    ]);
  }

  /**
   * {@inheritdoc}
   */
  public function getDescription() {
    return '';
  }

  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state, $node_revision = NULL, $langcode = NULL) {
    $this->langcode = $langcode;
    $form = parent::buildForm($form, $form_state, $node_revision);

    // Unless untranslatable fields are configured to affect only the default
    // translation, we need to ask the user whether they should be included in
    // the revert process.
    $default_translation_affected = $this->revision
      ->isDefaultTranslationAffectedOnly();
    $form['revert_untranslated_fields'] = [
      '#type' => 'checkbox',
      '#title' => $this
        ->t('Revert content shared among translations'),
      '#default_value' => $default_translation_affected && $this->revision
        ->getTranslation($this->langcode)
        ->isDefaultTranslation(),
      '#access' => !$default_translation_affected,
    ];
    return $form;
  }

  /**
   * {@inheritdoc}
   */
  protected function prepareRevertedRevision(NodeInterface $revision, FormStateInterface $form_state) {
    $revert_untranslated_fields = (bool) $form_state
      ->getValue('revert_untranslated_fields');
    $translation = $revision
      ->getTranslation($this->langcode);
    return $this->nodeStorage
      ->createRevision($translation, TRUE, $revert_untranslated_fields);
  }

}