anchor.diff:      context.dartSource = sample.dartCode;
       context.htmlSource = sample.htmlCode;
       context.cssSource = sample.cssCode;
  -    _backupRun();
  +    _storePreviousResult();
     }
   
     void showGist(RouteEnterEvent event) {
  
positive.code:     });
    }
  
    bool _requestStored() {
      return (_lastRun != null && _lastRun['dart'] == context.dartSource && _lastRun['html'] == context.htmlSource 
          &&  _lastRun['css'] == context.cssSource && _storedResponse != null);
    }
   
    void _backupRun() {
      var input = new CompileRequest()..source = context.dartSource;
      _setBackup();
      dartServices
          .compile(input)
          .timeout(longServiceCallTimeout)
          .then((CompileResponse response) {
        _storedResponse = response;
      });
    }
    
  
negative.code:   PaperIconButton _resetButton;
    PaperTabs _tabs;
  
    Map<String, String> _lastRun;
    Router _router;
    
    CompileResponse _cachedCompile;
    Editor editor;
    PlaygroundContext _context;
    Future _analysisRequest;
  