anchor.diff:        _current = null;
         return false;
       } else {
  -      _current = _cell.hashMapCellKey;
  +      _current = JS('', '#', _cell.hashMapCellKey);
         _cell = _cell._next;
         return true;
       }
  
positive.code:     LinkedHashMapCell cell = _first;
      int modifications = _modifications;
      while (cell != null) {
        action(cell.hashMapCellKey, cell.hashMapCellValue);
        if (modifications != _modifications) {
          throw new ConcurrentModificationError(this);
        }
  
negative.code:     LinkedHashMapCell cell = _map._first;
      int modifications = _map._modifications;
      while (cell != null) {
        f(JS('', '#', cell.hashMapCellKey));
        if (modifications != _map._modifications) {
          throw new ConcurrentModificationError(_map);
        }
  