function fulfillSoon(ctor, value) {
  return new ctor((resolve, reject) => {
    window.setTimeout(() => resolve(value), 0);
  });
}
Return an `IThenable` for `(typeof ctor)` that resolves on the next tick.

@template T
@param {function(new:T, ...?)} ctor
@param {?} value
@return {T}