setPrototypeOf should throw TypeError if typeof newProto === 'undefined'

[johnjbarton]

The first line of [[setPrototypeOf]] fails if the argument is undefined:
https://people.mozilla.org/~jorendorff/es6-draft.html#sec-ordinary-object-internal-methods-and-internal-slots-setprototypeof-v

But reflect.js does not:

  function testSetPrototypeOf() {
    var obj = {};
    var shouldThrow;
    try {
      Object.setPrototypeOf(obj, undefined);
    } catch (ex) {
      shouldThrow = ex;
    }
    assert(shouldThrow);
  }

I believe the issue here is that reflect.js implements Object.setPrototypeOf(obj, newProto) using obj.__proto__ setter, but somehow these operations are not consistent on Chrome at least.

[tvcutsem]

Reflect.setPrototypeOf now explicitly tests whether the new prototype is an object or null.