Add @@iterator for generator objects

test/mjsunit/harmony/generators-runtime.js

Index: test/mjsunit/harmony/generators-runtime.js
diff --git a/test/mjsunit/harmony/generators-runtime.js b/test/mjsunit/harmony/generators-runtime.js
index 196adff81b0ae586427115496e5c79b01822f513..9fb70754928e2ebe990694694a352cc4a9c9558d 100644
--- a/test/mjsunit/harmony/generators-runtime.js
+++ b/test/mjsunit/harmony/generators-runtime.js
@@ -29,9 +29,8 @@
 
 // Test aspects of the generator runtime.
 
-// FIXME(wingo): Replace this reference with a more official link.
 // See:
-// http://wiki.ecmascript.org/lib/exe/fetch.php?cache=cache&media=harmony:es6_generator_object_model_3-29-13.png
+// http://people.mozilla.org/~jorendorff/es6-draft.html#sec-generatorfunction-objects
 
 function f() { }
 function* g() { yield 1; }
@@ -101,6 +100,16 @@ function TestGeneratorObjectPrototype() {
   found_property_names.sort();
 
   assertArrayEquals(expected_property_names, found_property_names);
+
+  iterator_desc = Object.getOwnPropertyDescriptor(GeneratorObjectPrototype,
+      Symbol.iterator);
+  assertTrue(iterator_desc !== undefined);
+  assertFalse(iterator_desc.writable);
+  assertFalse(iterator_desc.enumerable);
+  assertFalse(iterator_desc.configurable);
+
+  // The generator object's "iterator" function is just the identity.
+  assertSame(iterator_desc.value.call(42), 42);
 }
 TestGeneratorObjectPrototype();