anchor.diff:  
   
   void _signalDoneLoading() native "Builtin_DoneLoading";
  +
  +void _cleanup() {
  +  if (_httpClient != null) {
  +    _httpClient.close();
  +    _httpClient = null;
  +  }
  +}
   
   void _loadScriptCallback(int tag, String uri, String libraryUri, List<int> data)
       native "Builtin_LoadScript";
  
positive.code:     var uri = userString.substring(_DART_EXT.length);
      return '$_DART_EXT${baseUri.resolve(uri)}';
    } else {
      return '${baseUri.resolve(userString)}';
    }
  }
  
  
negative.code:   _asyncLoadErrorCallback(uri, libraryUri, error);
    if (_numOutstandingLoadRequests == 0) {
      _signalDoneLoading();
      _cleanup();
    }
  }
  
  