Confusion on changing data property callback attributes

src/accessors.h

Index: src/accessors.h
diff --git a/src/accessors.h b/src/accessors.h
index d7296f2d83d198e75729e7fb146613b47456b2e4..ae748c5189897aaea5cd93ee43e3b3fdc4bb3391 100644
--- a/src/accessors.h
+++ b/src/accessors.h
@@ -86,6 +86,11 @@ class Accessors : public AllStatic {
       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);