Re-write tests for Promise.prototype internal slots

The original implementation of the test for the absense of a
[[PromiseState]] internal slot did not actually assert the documented
semantics. Re-implement the test to rely on the IsPromise abstract
operation (via `Promise.prototype.then`) to accurately ensure that the
object does not have a [[PromiseState]] internal slot.

In relying on the semantics of the `instanceof` operator, the original
test for the [[Prototype]] internal slot was imprecise (the assertion
could be satisfied if additional objects were incorrectly defined on the
prototype chain). Re-write the test to assert the value of the
[[Prototype]] internal slot directly.

test/built-ins/Promise/prototype/S25.4.5_A1.1_T1.js

@@ -1,14 +0,0 @@
-// Copyright 2014 Cubane Canada, Inc.  All rights reserved.
-// See LICENSE for details.
-
-/*---
-info: >
-    Promise prototype object is an ordinary object
-es6id: S25.4.5_A1.1_T1
-author: Sam Mikes
-description: Promise prototype does not have [[PromiseState]] internal slot
----*/
-
-assert.throws(TypeError, function() {
-  Promise.call(Promise.prototype, function () {});
-});

test/built-ins/Promise/prototype/S25.4.5_A2.1_T1.js

@@ -1,15 +0,0 @@
-// Copyright 2014 Cubane Canada, Inc.  All rights reserved.
-// See LICENSE for details.
-
-/*---
-info: >
-    Promise prototype object is an ordinary object
-es6id: S25.4.5_A2.1_T1
-author: Sam Mikes
-description: Promise prototype is a standard built-in Object
----*/
-
-if (!(Promise.prototype instanceof Object)) {
-    $ERROR("Expected Promise.prototype to be an Object");
-}
-

test/built-ins/Promise/prototype/no-promise-state.js

@@ -0,0 +1,27 @@
+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-properties-of-the-promise-prototype-object
+es6id: 25.4.5
+description: Promise.prototype does not have a [[PromiseState]] internal slot
+info: |
+  The Promise prototype object is the intrinsic object %PromisePrototype%. The
+  value of the [[Prototype]] internal slot of the Promise prototype object is
+  the intrinsic object %ObjectPrototype%. The Promise prototype object is an
+  ordinary object. It does not have a [[PromiseState]] internal slot or any of
+  the other internal slots of Promise instances.
+
+  25.4.5.3 Promise.prototype.then
+
+  1. Let promise be the this value.
+  2. If IsPromise(promise) is false, throw a TypeError exception.
+
+  25.4.1.6 IsPromise
+
+  1. If Type(x) is not Object, return false.
+  2. If x does not have a [[PromiseState]] internal slot, return false.
+---*/
+
+assert.throws(TypeError, function() {
+  Promise.prototype.then.call(Promise.prototype, function() {}, function() {});
+});

test/built-ins/Promise/prototype/proto.js

@@ -0,0 +1,15 @@
+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-properties-of-the-promise-prototype-object
+es6id: 25.4.5
+description: Promise.prototype [[Prototype]] is %ObjectPrototype%
+info: |
+  The Promise prototype object is the intrinsic object %PromisePrototype%. The
+  value of the [[Prototype]] internal slot of the Promise prototype object is
+  the intrinsic object %ObjectPrototype%. The Promise prototype object is an
+  ordinary object. It does not have a [[PromiseState]] internal slot or any of
+  the other internal slots of Promise instances.
+---*/
+
+assert.sameValue(Object.getPrototypeOf(Promise.prototype), Object.prototype);