anchor.diff:        e.text = description == null ? '' : description;
       }
     }
  -
  +  
  +  void _setBackup () {
  +    _lastRun = new Map();
  +    _lastRun['dart'] = context.dartSource;
  +    _lastRun['html'] = context.htmlSource;
  +    _lastRun['css'] = context.cssSource;
  +  }
  +  
     void _setGistId(String id) {
       if (id == null || id.isEmpty) {
         _gistId = null;
  
positive.code:       context.cssSource = css == null ? '' : css.content;
  
        _clearErrors();
  
        // Analyze and run it.
        Timer.run(() {
          _performAnalysis();
  
negative.code:     context.dartSource = sample.dartCode;
      context.htmlSource = sample.htmlCode;
      context.cssSource = sample.cssCode;
      _backupRun();
    }
  
    void showGist(RouteEnterEvent event) {
  