anchor.diff:    late final Splitter splitter;
   
     late final Console consoleExpandController;
  -  late final DElement webOutputLabel;
  +  DElement? webOutputLabel;
     late final DElement featureMessage;
   
     late final MDCLinearProgress linearProgress;
  
positive.code:   late final TabView editorTabView;
    late final TabView testTabView;
    late final TabView solutionTabView;
    late final TabView htmlTabView;
    late final TabView cssTabView;
    late final DElement solutionTab;
    late final MDCMenu menu;
  
  
negative.code: 
      // The iframe will show Flutter output for the rest of the lifetime of the
      // app, so hide the label.
      webOutputLabel?.setAttr('hidden');
  
      return success;
    }
  