docs: public final byte[] memOrLoad() {
      byte[] mem = _mem;          // Read once!
      if( mem != null ) return mem;
      Freezable pojo = _pojo;     // Read once!
      if( pojo != null )
        if( pojo instanceof Chunk ) return (_mem = ((Chunk)pojo).getBytes());
        else return (_mem = pojo.write(new AutoBuffer()).buf());
      if( _max == 0 ) return (_mem = new byte[0]);
      return (_mem = loadPersist());
    }