PointerDownEvent down(Point newLocation, { Duration timeStamp: Duration.ZERO })

Create a PointerDownEvent at the given location.

By default, the time stamp on the event is Duration.ZERO. You can give a specific time stamp by passing the timeStamp argument.

Source 

PointerDownEvent down(Point newLocation, { Duration timeStamp: Duration.ZERO }) {
  assert(!isDown);
  _isDown = true;
  _location = newLocation;
  return new PointerDownEvent(
    timeStamp: timeStamp,
    pointer: pointer,
    position: location
  );
}