anchor.diff:  
     void updatePushPermissionSwitch() {
       pushPermissionSwitch.checked = isPushEnabled;
  +  }
  +
  +  void _hideElement(Element el) {
  +    el.style.display = "none";
  +  }
  +
  +  void _showElement(Element el) {
  +    el.style.display = "block";
     }
   
     Future handlePushPermissionSwitchClick(_) async {
  
positive.code: import 'package:dart_service_worker/config.dart';
  import 'package:dart_service_worker/service_worker_client.dart';
  
  
  class MyServiceWorkerClientHelper extends ServiceWorkerClientHelper {
    CheckboxInputElement pushPermissionSwitch;
    Element filipMessageEl;
    Element filipMessageBubbleEl;
  
negative.code:     pushPermissionSwitch = querySelector("#push-permission-switch");
      filipMessageEl = querySelector("#filip-message");
      filipMessageBubbleEl = querySelector("#filip-message-bubble");
      subsPermissionDeniedEl =
          querySelector("#push-subscription-permission-denied");
      subsCountMessageEl = querySelector("#subscriptions-count-message");
    }
  
  