protected BackgroundTask(long timeout,TimeUnit timeUnit){
  this.ownerFrame=null;
  this.timeoutMilliseconds=timeUnit.toMillis(timeout);
}

protected BackgroundTask ( long timeout , TimeUnit timeUnit ) { this . ownerFrame = null ; this . timeoutMilliseconds = timeUnit . toMillis ( timeout ) ; }
create a task with timeout . < p / > the task will not be associated with any window .
