We will need this for https://github.com/popcodeorg/popcode/issues/1403 as well as AsyncMode for https://github.com/popcodeorg/popcode/issues/1394 (PR https://github.com/popcodeorg/popcode/pull/1426). 16.3 also adds the new lifecycle methods for Fiber. Quite a doozie!
