As used in the Workers’ Compensation Act, unless the context otherwise requires, where any employer procures any work to be done wholly or in part for him by a contractor other than an independent contractor and the work so procured to be done is a part or process in the trade or business or undertaking of such employer, then such employer shall be liable to pay all compensation under the Workers’ Compensation Act to the same extent as if the work were done without the intervention of such contractor. The work so procured to be done shall not be construed to be “casual employment”.