[es6] Define generator prototype as writable prop

test/mjsunit/harmony/object-literals-method.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --harmony-object-literals --allow-natives-syntax
 
 
 (function TestBasics() {
   var object = {
     method() {
@@ skipping 138 matching lines @@
   %OptimizeFunctionOnNextCall(object.method);
   assertEquals(42, object.method());
   assertFalse(object.method.hasOwnProperty('prototype'));
 })();
 
 
 ///////////////////////////////////////////////////////////////////////////////
 
 
 var GeneratorFunction = function*() {}.__proto__.constructor;
+var GeneratorPrototype = Object.getPrototypeOf(function*() {}).prototype;
 
 
 function assertIteratorResult(value, done, result) {
   assertEquals({value: value, done: done}, result);
 }
 
 
 (function TestGeneratorBasics() {
   var object = {
     *method() {
@@ skipping 39 matching lines @@
   assertTrue(desc.configurable);
   assertTrue(desc.writable);
   assertEquals('function', typeof desc.value);
 
   var g = desc.value();
   assertIteratorResult(1, false, g.next());
   assertIteratorResult(undefined, true, g.next());
 })();
 
 
+(function TestGeneratorPrototypeDescriptor() {
+  var object = {
+    *method() {}
+  };
+
+  var desc = Object.getOwnPropertyDescriptor(object.method, 'prototype');
+  assertFalse(desc.enumerable);
+  assertFalse(desc.configurable);
+  assertTrue(desc.writable);
+  assertEquals(GeneratorPrototype, Object.getPrototypeOf(desc.value));
+})();
+
+
 (function TestGeneratorProto() {
   var object = {
     *method() {}
   };
 
   assertEquals(GeneratorFunction.prototype,
                Object.getPrototypeOf(object.method));
 })();
 
 
@@ skipping 63 matching lines @@
   var p = {};
   var object = {
     __proto__() {
       return 1;
     },
     __proto__: p
   };
   assertEquals(p, Object.getPrototypeOf(object));
   assertEquals(1, object.__proto__());
 })();