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