Introduce JSFunction::EnsureHasInitialMap method.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index e0f160ba2b312981affdd1a3d220baf3ae3e4069..527a6ebc9569f579188bc93091c51d60d7ebd04f 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -9892,6 +9892,15 @@ void JSFunction::RemovePrototype() {
 }
 
 
+void JSFunction::EnsureHasInitialMap(Handle<JSFunction> function) {
+  if (function->has_initial_map()) return;
+  Isolate* isolate = function->GetIsolate();
+  Handle<Map> initial_map = isolate->factory()->NewInitialMap(function);
+  function->set_initial_map(*initial_map);
+  initial_map->set_constructor(*function);
+}
+
+
 void JSFunction::SetInstanceClassName(String* name) {
   shared()->set_instance_class_name(name);
 }