anchor.diff:    PaperIconButton _resetButton;
     PaperTabs _tabs;
   
  -  Map _lastRun;
  +  Map<String, String> _lastRun;
     Router _router;
     
  -  CompileResponse _storedResponse;
  +  CompileResponse _cachedCompile;
     Editor editor;
     PlaygroundContext _context;
     Future _analysisRequest;
  
positive.code:       String id = url.queryParameters['id'];
        if (isLegalGistId(id)) {
          _showGist(id);
          _backupRun();
          return;
        }
      }
  
negative.code:   }
    
    void _setBackup () {
      _lastRun = new Map<String, String>();
      _lastRun['dart'] = context.dartSource;
      _lastRun['html'] = context.htmlSource;
      _lastRun['css'] = context.cssSource;
  