Create pre-frozen change records for Object.observe

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 46539311de9625d9c7ffccc54bd476ab5510a47b..1ca7cc7790735709fea979a1d6f7300302ca6be1 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -1750,15 +1750,40 @@ void JSObject::EnqueueChangeRecord(Handle<JSObject> object,
   Isolate* isolate = object->GetIsolate();
   HandleScope scope;
   Handle<String> type = isolate->factory()->LookupUtf8Symbol(type_str);
-  if (object->IsJSGlobalObject()) {
+  EnqueueChangeRecord(object, type, name, old_value);
+}
+
+void JSObject::EnqueueChangeRecord(Handle<JSObject> object,
+                                   Handle<String> type,
+                                   Handle<String> name,
+                                   Handle<Object> old_value) {
+  Isolate* isolate = object->GetIsolate();
+  HandleScope scope;
+  if (object->IsJSGlobalObject())
     object = handle(JSGlobalObject::cast(*object)->global_receiver(), isolate);
+  Handle<JSObject> change_record = isolate->factory()->NewJSObjectFromMap(
+      old_value->IsTheHole()
+      ? isolate->change_record_map()
+      : isolate->change_record_oldvalue_map());
+
+  // Make sure both properties and elements are frozen.
+  ASSERT(!change_record->map()->is_extensible());
+  Handle<SeededNumberDictionary> elements = NormalizeElements(change_record);
+  elements->set_requires_slow_elements();
+
+  change_record->InObjectPropertyAtPut(JSChangeRecord::kTypeIndex, *type);
+  change_record->InObjectPropertyAtPut(JSChangeRecord::kObjectIndex, *object);
+  change_record->InObjectPropertyAtPut(JSChangeRecord::kNameIndex, *name);
+  if (!old_value->IsTheHole()) {
+    change_record->InObjectPropertyAtPut(
+        JSChangeRecord::kOldValueIndex, *old_value);
   }
-  Handle<Object> args[] = { type, object, name, old_value };
+
+  Handle<Object> args[] = { change_record };
   bool threw;
-  Execution::Call(Handle<JSFunction>(isolate->observers_notify_change()),
-                  Handle<Object>(isolate->heap()->undefined_value()),
-                  old_value->IsTheHole() ? 3 : 4, args,
-                  &threw);
+  Execution::Call(isolate->observers_notify_change(),
+                  isolate->factory()->undefined_value(),
+                  1, args, &threw);
   ASSERT(!threw);
 }
 
@@ -9414,12 +9439,10 @@ MaybeObject* JSArray::SetElementsLength(Object* len) {
   CHECK(self->length()->ToArrayIndex(&new_length));
   if (old_length != new_length) {
     for (int i = 0; i < indices.length(); ++i) {
-      JSObject::EnqueueChangeRecord(
-          self, "deleted", indices[i], old_values[i]);
+      EnqueueChangeRecord(self, "deleted", indices[i], old_values[i]);
     }
-    JSObject::EnqueueChangeRecord(
-        self, "updated", isolate->factory()->length_symbol(),
-        old_length_handle);
+    EnqueueChangeRecord(self, "updated", isolate->factory()->length_symbol(),
+                        old_length_handle);
   }
   return *hresult;
 }