Issue #3316136 by julien.sibi, flocondetoile: LanguageNegotiationInterface.php...

 * }

 *

 * class MyLanguageNegotiationUrl extends LanguageNegotiationUrl {

 *   public function getCurrentLanguage(Request $request = NULL) {

 *   public function getLangcode(Request $request = NULL) {

 *     if ($request) {

 *       // Use the original URL language negotiation method to get a valid

 *       // language code.

 *       $langcode = parent::getCurrentLanguage($request);

 *       $langcode = parent::getLangcode($request);

 *

 *       // If we are on an administrative path, override with the default

 *       language.