_ShiftPartOfRegion
void _ShiftPartOfRegion(BRegion* region,
_ShiftPartOfRegion(&fDirtyRegion, region, xOffset, yOffset);
_ShiftPartOfRegion(&fCurrentUpdateSession.DirtyRegion(), region, xOffset, yOffset);
_ShiftPartOfRegion(&fPendingUpdateSession.DirtyRegion(), region, xOffset, yOffset);
void _ShiftPartOfRegion(BRegion* region, BRegion* regionToShift,