Function updateFragment

docs/external/js/react-dom.development.js:13735–13747

(returnFiber, current, fragment, expirationTime, key)

    }

    function updateFragment(returnFiber, current, fragment, expirationTime, key) {
      if (current === null || current.tag !== Fragment) {
        // Insert
        var created = createFiberFromFragment(fragment, returnFiber.mode, expirationTime, key);
        created.return = returnFiber;
        return created;
      } else {
        // Update
        var existing = useFiber(current, fragment);
        existing.return = returnFiber;
        return existing;
      }
    }

    function createChild(returnFiber, newChild, expirationTime) {
      if (typeof newChild === 'string' || typeof newChild === 'number') {