Hanldify JSObject::PreventExtensions method.

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 2513 matching lines @@
   // to ensure that |filler_value| can be collected without WB here.
   inline void InitializeBody(Map* map,
                              Object* pre_allocated_value,
                              Object* filler_value);
 
   // Check whether this object references another object
   bool ReferencesObject(Object* obj);
 
   // Disalow further properties to be added to the object.
   static Handle<Object> PreventExtensions(Handle<JSObject> object);
-  MUST_USE_RESULT MaybeObject* PreventExtensions();
 
   // ES5 Object.freeze
   static Handle<Object> Freeze(Handle<JSObject> object);
 
   // Called the first time an object is observed with ES7 Object.observe.
   MUST_USE_RESULT MaybeObject* SetObserved(Isolate* isolate);
 
   // Copy object.
   static Handle<JSObject> Copy(Handle<JSObject> object);
   static Handle<JSObject> DeepCopy(Handle<JSObject> object);
@@ skipping 7687 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_