anchor.diff:    Future<void> _format() {
       var originalSource = context.dartSource;
       var input = SourceRequest()..source = originalSource;
  -    formatButton.disabled = true;
  +    _formatButton.disabled = true;
   
       var request = dartServices.format(input).timeout(serviceCallTimeout);
       return request.then((FormatResponse result) {
         busyLight.reset();
  -      formatButton.disabled = false;
  +      _formatButton.disabled = false;
   
         if (result.newString.isEmpty) {
           _logger.fine('Format returned null/empty result');
  
positive.code: }
  
  class Playground extends EditorUi implements GistContainer, GistController {
    final MutableGist editableGist = MutableGist(Gist());
    late GistStorage _gistStorage;
    late MDCButton newButton;
    late MDCButton resetButton;
    late MDCButton formatButton;
    late MDCButton installButton;
    late MDCButton samplesButton;
    late MDCButton editorConsoleTab;
    late MDCButton editorDocsTab;
    late MDCButton closePanelButton;
    late MDCButton moreMenuButton;
    late DElement editorPanelHeader;
    late DElement editorPanelFooter;
    late MDCMenu samplesMenu;
    late MDCMenu moreMenu;
    late NewPadDialog newPadDialog;
    late DElement titleElement;
    late MaterialTabController webLayoutTabController;
    late DElement webTabBar;
    late DElement webOutputLabel;
    late MDCSwitch nullSafetySwitch;
  
    late Splitter splitter;
    late Splitter rightSplitter;
    bool rightSplitterConfigured = false;
    TabExpandController? tabExpandController;
  
    @override
    late PlaygroundContext context;
    Layout? _layout;
  
    // The last returned shared gist used to update the url.
    Gist? _overrideNextRouteGist;
    late DocHandler docHandler;
  
    late Console _leftConsole;
    late Console _rightConsole;
    late Counter unreadConsoleCounter;
  
    Playground() {
      _initDialogs();
  
negative.code:   void _initConsoles() {
      _leftConsole = Console(DElement(_leftConsoleElement));
      _rightConsole = Console(DElement(_rightConsoleContentElement));
      _unreadConsoleCounter =
          Counter(querySelector('#unread-console-counter') as SpanElement);
    }
  
  