Confusion on changing data property callback attributes

src/objects-inl.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.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 6402 matching lines @@
 }
 
 
 bool AccessorInfo::IsCompatibleReceiver(Object* receiver) {
   Object* function_template = expected_receiver_type();
   if (!function_template->IsFunctionTemplateInfo()) return true;
   return FunctionTemplateInfo::cast(function_template)->IsTemplateFor(receiver);
 }
 
 
+void ExecutableAccessorInfo::clear_setter() {
+  set_setter(GetIsolate()->heap()->undefined_value(), SKIP_WRITE_BARRIER);
+}
+
+
 void AccessorPair::set_access_flags(v8::AccessControl access_control) {
   int current = access_flags()->value();
   current = BooleanBit::set(current,
                             kProhibitsOverwritingBit,
                             access_control & PROHIBITS_OVERWRITING);
   current = BooleanBit::set(current,
                             kAllCanReadBit,
                             access_control & ALL_CAN_READ);
   current = BooleanBit::set(current,
                             kAllCanWriteBit,
@@ skipping 431 matching lines @@
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_