private void tryShutdown(){
  if (isClosing() && isOkToClose())   shutdown(closeFuture.get());
}

private void tryShutdown ( ) { if ( isClosing ( ) && isOkToClose ( ) ) shutdown ( closeFuture . get ( ) ) ; }
close was signaled in closeasync ( ) but there were pending messages at that time . this method attempts the shutdown if the returned result cleared up the last pending message .
