Whenever heretofore the county commissioners of any county have fixed the compensation of tax collectors of boroughs and townships of the second class and of treasurers of townships of the first class for collecting county and county institution district taxes at an amount, not exceeding five per centum (5%) of the amount collected, such action of the county commissioners is hereby validated and made binding and effective upon the county and the county institution district, to the same extent as though the action had been taken pursuant to the provisions of pre-existing law.