Confusion on changing data property callback attributes

src/accessors.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_ACCESSORS_H_
 #define V8_ACCESSORS_H_
 
 #include "allocation.h"
 #include "v8globals.h"
 
@@ skipping 68 matching lines @@
                                       Handle<String> name,
                                       int* object_offset);
 
   static Handle<AccessorInfo> MakeAccessor(
       Isolate* isolate,
       Handle<String> name,
       AccessorGetterCallback getter,
       AccessorSetterCallback setter,
       PropertyAttributes attributes);
 
+  static Handle<ExecutableAccessorInfo> CloneAccessor(
+      Isolate* isolate,
+      Handle<ExecutableAccessorInfo> accessor);
+
+
  private:
   // Helper functions.
   static Handle<Object> FlattenNumber(Isolate* isolate, Handle<Object> value);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ACCESSORS_H_