anchor.diff:      context.onModeChange.listen((_) => docHandler.generateDoc(_docPanel));
   
       // Bind the editable files to the gist.
  -    Property htmlFile =
  -        new GistFileProperty(editableGist.getGistFile('index.html'))
  -      ..onChanged
  -          .listen((html) => _checkForEmptyHtml(html == null ? "" : html));
  -    Property htmlDoc =
  -        new EditorDocumentProperty(_context.htmlDocument, 'html');
  +    Property htmlFile = new GistFileProperty(editableGist.getGistFile('index.html'));
  +    Property htmlDoc = new EditorDocumentProperty(_context.htmlDocument, 'html');
       bind(htmlDoc, htmlFile);
       bind(htmlFile, htmlDoc);
   
  -    Property cssFile =
  -        new GistFileProperty(editableGist.getGistFile('styles.css'));
  +    Property cssFile = new GistFileProperty(editableGist.getGistFile('styles.css'));
       Property cssDoc = new EditorDocumentProperty(_context.cssDocument, 'css');
       bind(cssDoc, cssFile);
       bind(cssFile, cssDoc);
   
  -    Property dartFile =
  -        new GistFileProperty(editableGist.getGistFile('main.dart'));
  -    Property dartDoc =
  -        new EditorDocumentProperty(_context.dartDocument, 'dart');
  +    Property dartFile = new GistFileProperty(editableGist.getGistFile('main.dart'));
  +    Property dartDoc = new EditorDocumentProperty(_context.dartDocument, 'dart');
       bind(dartDoc, dartFile);
       bind(dartFile, dartDoc);
   
  
positive.code:   IFrameElement get _frame => querySelector('#frame');
    bool get _isCompletionActive => editor.completionActive;
    DivElement get _docPanel => querySelector('#documentation');
    bool _htmlIsEmpty = true;
  
    DButton runButton;
    DOverlay overlay;
  
negative.code:       runButton.disabled = false;
        overlay.visible = false;
      });
    }
  
    /// Switch to the console or html results tab depending on whether the sample
    /// has html content or not.
    void _switchOutputTab(String html) {
      if (html.trim().isEmpty) {
        outputTabController.selectTab("console");
      } else {
        outputTabController.selectTab("result");
      }
    }
  
    Future<String> _createSummary() {
  