Ensure that collection iterators' maps have constructors

This fixes JSObject::GetCreationContext() for such iterators.

R=rossberg@chromium.org

Review URL: https://codereview.chromium.org/288233002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21333 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/bootstrapper.cc

@@ -1314,11 +1314,13 @@ void Genesis::InitializeExperimentalGlobal() {
     {   // -- S e t I t e r a t o r
       Handle<Map> map = isolate()->factory()->NewMap(
           JS_SET_ITERATOR_TYPE, JSSetIterator::kSize);
+      map->set_constructor(native_context()->closure());
       native_context()->set_set_iterator_map(*map);
     }
     {   // -- M a p I t e r a t o r
       Handle<Map> map = isolate()->factory()->NewMap(
           JS_MAP_ITERATOR_TYPE, JSMapIterator::kSize);
+      map->set_constructor(native_context()->closure());
       native_context()->set_map_iterator_map(*map);
     }
   }