[runtime] Stop cloning AccessorInfo, just rely on PropertyAttributes for readonly.

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 "include/v8.h"
 #include "src/allocation.h"
 #include "src/globals.h"
@@ skipping 82 matching lines @@
   static bool IsJSArrayBufferViewFieldAccessor(Handle<Map> map,
                                                Handle<Name> name,
                                                int* object_offset);
 
   static Handle<AccessorInfo> MakeAccessor(
       Isolate* isolate,
       Handle<Name> name,
       AccessorNameGetterCallback getter,
       AccessorNameSetterCallback setter,
       PropertyAttributes attributes);
-
-  static Handle<AccessorInfo> CloneAccessor(Isolate* isolate,
-                                            Handle<AccessorInfo> accessor);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ACCESSORS_H_