Aft, because the lift due to the flap increases the proportion of the total lift that is produced by the aft section of the wing.
However:
The change in pitching moment for the whole aircraft can be nose up, neutral or nose down. This is due to the interaction of the change in downwash over the tail, the increase and vertical displacement of the total drag line and the sweep of the wing, in addition to the increase and aft movement of the lift vector.