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

src/lookup.cc

Index: src/lookup.cc
diff --git a/src/lookup.cc b/src/lookup.cc
index b66d67519cc1e334f2008a7794d9be9ab68e8624..b99bf4037ba8e1f6f1d10993dc21e15ef305b094 100644
--- a/src/lookup.cc
+++ b/src/lookup.cc
@@ -606,9 +606,8 @@ LookupIterator::State LookupIterator::LookupInHolder(Map* const map,
         // Do not leak private property names.
         if (IsElement() || !name_->IsPrivate()) return JSPROXY;
       }
-      if (map->is_access_check_needed() &&
-          (IsElement() || !isolate_->IsInternallyUsedPropertyName(name_))) {
-        return ACCESS_CHECK;
+      if (map->is_access_check_needed()) {
+        if (IsElement() || !name_->IsPrivate()) return ACCESS_CHECK;
       }
     // Fall through.
     case ACCESS_CHECK: