Fix JSFunction's in-object properties initialization.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 4b6c63e0c9606be9ddeb9f86acc2ef4dfc14e19b..055d0d7f1f5e74047214381593df045510a814e2 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -1728,6 +1728,10 @@ class Heap {
   // Initializes a JSObject based on its map.
   void InitializeJSObjectFromMap(JSObject* obj, FixedArray* properties,
                                  Map* map);
+
+  // Initializes JSObject body starting at given offset.
+  void InitializeJSObjectBody(JSObject* obj, Map* map, int start_offset);
+
   void InitializeAllocationMemento(AllocationMemento* memento,
                                    AllocationSite* allocation_site);