Issue #3496607 by alexpott: Make return value of stopEvent consistent and the...

      xhr.getResponseHeader('X-Drupal-Ajax-Token') === '1' &&

      // The isInProgress() function might not be defined if the Ajax request

      // was initiated without Drupal.ajax() or new Drupal.Ajax().

      settings.isInProgress &&

      typeof settings.isInProgress === 'function' &&

      // Until this is false, the Ajax request isn't completely done (the

      // response's commands might still be running).

      settings.isInProgress()