anchor.diff:    // NOTE: When maps are deserialized, their _index and _hashMask is regenerated
     // lazily by _regenerateIndex.
     // TODO(koda): Consider also using null _index for tiny, linear-search tables.
  -  Uint32List _index;
  +  Uint32List _index = new Uint32List(_HashBase._INITIAL_INDEX_SIZE);
   
     // Cached in-place mask for the hash pattern component. 
  -  int _hashMask;
  +  int _hashMask = _HashBase._indexSizeToHashMask(_HashBase._INITIAL_INDEX_SIZE);
   
     // Fixed-length list of keys (set) or key/value at even/odd indices (map).
     List _data;
  
positive.code: 
    // Number of deleted keys.
    int _deletedKeys = 0;
  }
  
  // Base class for VM-internal classes; keep in sync with _HashFieldBase.
  
negative.code:          _IdenticalAndIdentityHashCode
      implements LinkedHashMap<K, V> {
  
    _CompactLinkedIdentityHashMap() : super(_HashBase._INITIAL_INDEX_SIZE);
  }
  
  class _CompactLinkedCustomHashMap<K, V> extends _HashFieldBase
  