/**
  * Add dynamic l10n js
  *
  * @return string URL of JS file
  */
 private function addLocalizationJs()
 {
     $config = CRM_Core_Config::singleton();
     $fileName = 'l10n-' . $config->lcMessages . '.js';
     if (!is_file(CRM_Utils_File::dynamicResourcePath($fileName))) {
         CRM_Utils_File::addDynamicResource($fileName, $this->createLocalizationJs());
     }
     // Dynamic localization script
     return CRM_Utils_File::dynamicResourceUrl($fileName);
 }