anchor.diff:  }
   
   class LinkedHashMapKeyIterator<E> implements Iterator<E> {
  -  final dynamic/*=JsLinkedHashMap<E, dynamic>*/ _map;
  +  final dynamic _map;
     final int _modifications;
  -  LinkedHashMapCell/*<E, dynamic>*/ _cell;
  +  LinkedHashMapCell _cell;
     E _current;
   
     LinkedHashMapKeyIterator(this._map, this._modifications) {
  
positive.code: 
    V _removeHashTableEntry(var table, Object key) {
      if (table == null) return null;
      LinkedHashMapCell/*<K, V>*/ cell = _getTableCell(table, key);
      if (cell == null) return null;
      _unlinkCell(cell);
      _deleteTableEntry(table, key);
  
negative.code: 
    // The keys and values are stored in cells that are linked together
    // to form a double linked list.
    LinkedHashMapCell _first;
    LinkedHashMapCell _last;
  
    // We track the number of modifications done to the key set of the
    // hash map to be able to throw when the map is modified while being
  