[es6] silence access-check failure for well-known symbol properties

src/objects.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_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 1193 matching lines @@
   MUST_USE_RESULT static MaybeHandle<Object> BitwiseOr(
       Isolate* isolate, Handle<Object> lhs, Handle<Object> rhs,
       Strength strength = Strength::WEAK);
   MUST_USE_RESULT static MaybeHandle<Object> BitwiseXor(
       Isolate* isolate, Handle<Object> lhs, Handle<Object> rhs,
       Strength strength = Strength::WEAK);
 
   MUST_USE_RESULT static MaybeHandle<Object> GetProperty(
       LookupIterator* it, LanguageMode language_mode = SLOPPY);
 
+  // GetProperty, but allows custom behaviour when an access check fails
+  MUST_USE_RESULT static MaybeHandle<Object> GetPropertyEx(
+      LookupIterator* it, bool& access_check_failed,
+      LanguageMode language_mode = SLOPPY);
+
   // Implementation of [[Put]], ECMA-262 5th edition, section 8.12.5.
   MUST_USE_RESULT static MaybeHandle<Object> SetProperty(
       Handle<Object> object, Handle<Name> name, Handle<Object> value,
       LanguageMode language_mode,
       StoreFromKeyed store_mode = MAY_BE_STORE_FROM_KEYED);
 
   MUST_USE_RESULT static MaybeHandle<Object> SetProperty(
       LookupIterator* it, Handle<Object> value, LanguageMode language_mode,
       StoreFromKeyed store_mode);
 
@@ skipping 9399 matching lines @@
   Handle<FixedArray> keys_;
   Handle<OrderedHashSet> set_;
   int length_;
   DISALLOW_COPY_AND_ASSIGN(KeyAccumulator);
 };
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_