Add test for well-known Symbol, @@iterator

test/built-ins/Symbol/iterator/prop-desc.js

@@ -0,0 +1,17 @@
+// Copyright (C) 2015 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+es6id: 19.4.2.4
+description: >
+    `Symbol.iterator` property descriptor
+info: >
+    This property has the attributes { [[Writable]]: false, [[Enumerable]]:
+    false, [[Configurable]]: false }.
+includes: [propertyHelper.js]
+features: [Symbol.iterator]
+---*/
+
+assert.sameValue(typeof Symbol.iterator, 'symbol');
+verifyNotEnumerable(Symbol, 'iterator');
+verifyNotWritable(Symbol, 'iterator');
+verifyNotConfigurable(Symbol, 'iterator');