[es6] Define generator prototype as writable prop

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

Index: test/mjsunit/harmony/object-literals-method.js
diff --git a/test/mjsunit/harmony/object-literals-method.js b/test/mjsunit/harmony/object-literals-method.js
index 535231ea62f3bf642074eba74c516d48ea2626aa..d2879ada8f7ca59d8ecb7ea515cdfb8459ac4243 100644
--- a/test/mjsunit/harmony/object-literals-method.js
+++ b/test/mjsunit/harmony/object-literals-method.js
@@ -156,6 +156,7 @@
 
 
 var GeneratorFunction = function*() {}.__proto__.constructor;
+var GeneratorPrototype = Object.getPrototypeOf(function*() {}).prototype;
 
 
 function assertIteratorResult(value, done, result) {
@@ -215,6 +216,19 @@ function assertIteratorResult(value, done, result) {
 })();
 
 
+(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() {}