Use a wrapper for copying object.

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2129 matching lines @@
       PropertyAttributes attributes,
       StrictMode strict_mode,
       StoreFromKeyed store_from_keyed);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSReceiver);
 };
 
 // Forward declaration for JSObject::GetOrCreateHiddenPropertiesHashTable.
 class ObjectHashTable;
 
+// Forward declaration for JSObject::Copy.
+class AllocationSite;
+
+
 // The JSObject describes real heap allocated JavaScript objects with
 // properties.
 // Note that the map of JSObject changes during execution to enable inline
 // caching.
 class JSObject: public JSReceiver {
  public:
   // [properties]: Backing storage for properties.
   // properties is a FixedArray in the fast case and a Dictionary in the
   // slow case.
   DECL_ACCESSORS(properties, FixedArray)  // Get and set fast properties.
@@ skipping 488 matching lines @@
 
   // Called the first time an object is observed with ES7 Object.observe.
   static void SetObserved(Handle<JSObject> object);
 
   // Copy object.
   enum DeepCopyHints {
     kNoHints = 0,
     kObjectIsShallowArray = 1
   };
 
+  static Handle<JSObject> Copy(Handle<JSObject> object,
+                               Handle<AllocationSite> site);
   static Handle<JSObject> Copy(Handle<JSObject> object);
   static Handle<JSObject> DeepCopy(Handle<JSObject> object,
                                    AllocationSiteUsageContext* site_context,
                                    DeepCopyHints hints = kNoHints);
   static Handle<JSObject> DeepWalk(Handle<JSObject> object,
                                    AllocationSiteCreationContext* site_context);
 
   static Handle<Object> GetDataProperty(Handle<JSObject> object,
                                         Handle<Name> key);
 
@@ skipping 8387 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_