code: public ByteSink getByteSink()
      {
          ByteSink bs = byteSink;
          if ( progressListener != null ) {
              bs = new ProgressByteSink( bs, progressListener );
          }
          return bs;
      }
docs: If no progress listener has been set, return the byte sink defined in constructor, otherwise decorate it.
  
  @return the byte sink to be used for download operations.