Add debug mirror support for ES6 Map/Set iterators.

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 5713f73160c0ad312c8c2e9bbc90dbeaa94da3ec..72974a317c18646800178b4c10340a85b444afcf 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -1722,6 +1722,22 @@ Handle<JSDataView> Factory::NewJSDataView() {
 }
 
 
+Handle<JSMapIterator> Factory::NewJSMapIterator() {
+  Handle<Map> map(isolate()->native_context()->map_iterator_map());
+  CALL_HEAP_FUNCTION(isolate(),
+                     isolate()->heap()->AllocateJSObjectFromMap(*map),
+                     JSMapIterator);
+}
+
+
+Handle<JSSetIterator> Factory::NewJSSetIterator() {
+  Handle<Map> map(isolate()->native_context()->set_iterator_map());
+  CALL_HEAP_FUNCTION(isolate(),
+                     isolate()->heap()->AllocateJSObjectFromMap(*map),
+                     JSSetIterator);
+}
+
+
 namespace {
 
 ElementsKind GetExternalArrayElementsKind(ExternalArrayType type) {