Upon the adoption of a resolution therefor by a majority vote of the members-elect of the board of supervisors of any county now or hereafter having a population of 1,000,000 or more, according to the latest or each succeeding federal decennial census, the question of adopting the county civil service system, as provided for in this act, shall be submitted to a vote of the electors of such county. The question shall be submitted and placed on the ballot at the next general or special election.