code: public final byte[] memOrLoad() {
      byte[] mem = _mem;          // Read once!
      if( mem != null ) return mem;
      Freezable pojo = _pojo;     // Read once!
      if( pojo != null )          // Has the POJO, make raw bytes
        return _mem = pojo.asBytes();
      if( _max == 0 ) return (_mem = new byte[0]);
      return (_mem = loadPersist());
    }
docs: The FAST path get-byte-array - final method for speed.  Will (re)build
  the mem array from either the POJO or disk.  Never returns NULL.
  @return byte[] holding the serialized POJO