ExtendStorageStub added, it is aimed for extending objects backing store when it runs out of space.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index cc685577ce37cb029d57c98fb058bcd919fcc3bc..9dede11e2f5334412526c2e60b036ee171d2fc9d 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -1962,7 +1962,7 @@ void JSObject::MigrateFastToFast(Handle<JSObject> object, Handle<Map> new_map) {
     }
 
     DCHECK(number_of_fields == old_number_of_fields + 1);
-    // This migration is a transition from a map that has run out out property
+    // This migration is a transition from a map that has run out of property
     // space. Therefore it could be done by extending the backing store.
     Handle<FixedArray> old_storage = handle(object->properties(), isolate);
     Handle<FixedArray> new_storage =
@@ -3742,15 +3742,6 @@ bool JSObject::TryMigrateInstance(Handle<JSObject> object) {
 }
 
 
-void JSObject::MigrateToNewProperty(Handle<JSObject> object,
-                                    Handle<Map> map,
-                                    Handle<Object> value) {
-  JSObject::MigrateToMap(object, map);
-  if (map->GetLastDescriptorDetails().type() != FIELD) return;
-  object->WriteToField(map->LastAdded(), *value);
-}
-
-
 void JSObject::WriteToField(int descriptor, Object* value) {
   DisallowHeapAllocation no_gc;