Calling a generator function returns a generator object

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index 8695bcd5200af443291344d67e658999092749f7..2ef515aa4f714c0c9afaa5223ba41f3a8f656db4 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -286,6 +286,10 @@ class Factory {
   Handle<JSObject> NewJSObjectFromMap(Handle<Map> map,
                                       PretenureFlag pretenure = NOT_TENURED);
 
+  // JS generator iterators are not pretenured.
+  Handle<JSGeneratorIterator> NewJSGeneratorIterator(
+      Handle<JSFunction> function);
+
   // JS modules are pretenured.
   Handle<JSModule> NewJSModule(Handle<Context> context,
                                Handle<ScopeInfo> scope_info);