In the event that a development adjoins or includes existing Borough streets that do not conform to widths as shown on either the Master Plan or Official Map or the street width requirements of this chapter, additional land along one or both sides of the street shall be donated to the Borough for widening the street to meet the width shown on the Master Plan or Official Map. If the subdivision is along one side of the street only, 1/2 of the required extra width shall be provided.