ImportForm::submitForm

public ImportForm::submitForm(array &$form, FormStateInterface $form_state)

public function submitForm(array &$form, FormStateInterface $form_state) {
  \Drupal::moduleHandler()->loadInclude('locale', 'translation.inc');
  // Add language, if not yet supported.
  $language = $this->languageManager->getLanguage($form_state->getValue('langcode'));
  if (empty($language)) {
    $language = ConfigurableLanguage::createFromLangcode($form_state->getValue('langcode'));
    $language->save();
    drupal_set_message($this->t('The language %language has been created.', array('%language' => $this->t($language->label()))));
  }
  $options = array_merge(_locale_translation_default_update_options(), array(
    'langcode' => $form_state->getValue('langcode'),
    'overwrite_options' => $form_state->getValue('overwrite_options'),
    'customized' => $form_state->getValue('customized') ? LOCALE_CUSTOMIZED : LOCALE_NOT_CUSTOMIZED,
  ));
  $this->moduleHandler->loadInclude('locale', 'bulk.inc');
  $file = locale_translate_file_attach_properties($this->file, $options);
  $batch = locale_translate_batch_build(array($file->uri => $file), $options);
  batch_set($batch);

  // Create or update all configuration translations for this language.
  \Drupal::moduleHandler()->loadInclude('locale', 'bulk.inc');
  if ($batch = locale_config_batch_update_components($options, array($form_state->getValue('langcode')))) {
    batch_set($batch);
  }

  $form_state->setRedirect('locale.translate_page');
}