[runtime] Replace hidden_string with a 0-hash-code private symbol

src/lookup.h

 // Copyright 2014 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_LOOKUP_H_
 #define V8_LOOKUP_H_
 
 #include "src/factory.h"
 #include "src/isolate.h"
 #include "src/objects.h"
@@ skipping 191 matching lines @@
     return (configuration_ & kPrototypeChain) != 0;
   }
 
   /* ACCESS_CHECK */
   bool HasAccess() const;
 
   /* PROPERTY */
   bool ExtendingNonExtensible(Handle<JSObject> receiver) {
     DCHECK(receiver.is_identical_to(GetStoreTarget()));
     return !receiver->map()->is_extensible() &&
-           (IsElement() || !isolate_->IsInternallyUsedPropertyName(name_));
+           (IsElement() || !name_->IsPrivate());
   }
   void PrepareForDataProperty(Handle<Object> value);
   void PrepareTransitionToDataProperty(Handle<JSObject> receiver,
                                        Handle<Object> value,
                                        PropertyAttributes attributes,
                                        Object::StoreFromKeyed store_mode);
   bool IsCacheableTransition() {
     DCHECK_EQ(TRANSITION, state_);
     return transition_->IsPropertyCell() ||
            (!transition_map()->is_dictionary_map() &&
@@ skipping 113 matching lines @@
   Handle<JSReceiver> holder_;
   const Handle<JSReceiver> initial_holder_;
   uint32_t number_;
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_LOOKUP_H_