stream.defaultReadObject();
    int size = stream.readInt();
    init(16); // resist hostile attempts to allocate gratuitous heap
    Serialization.populateMap(this, stream, size);
  }

  @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;

    stream.defaultReadObject();
    int size = stream.readInt();
    init(16); // resist hostile attempts to allocate gratuitous heap
    Serialization.populateMap(this, stream, size);
  }

  // TODO(cpovirk): Should we have a serialVersionUID here?