Treat failed access checks for @@toStringTag as undefined

src/heap/heap.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_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 346 matching lines @@
 
 #define PUBLIC_SYMBOL_LIST(V)                 \
   V(has_instance_symbol, Symbol.hasInstance)  \
   V(is_regexp_symbol, Symbol.isRegExp)        \
   V(iterator_symbol, Symbol.iterator)         \
   V(match_symbol, Symbol.match)               \
   V(replace_symbol, Symbol.replace)           \
   V(search_symbol, Symbol.search)             \
   V(split_symbol, Symbol.split)               \
   V(to_primitive_symbol, Symbol.toPrimitive)  \
-  V(to_string_tag_symbol, Symbol.toStringTag) \
   V(unscopables_symbol, Symbol.unscopables)
 
 // Well-Known Symbols are "Public" symbols, which have a bit set which causes
 // them to produce an undefined value when a load results in a failed access
 // check. Because this behaviour is not specified properly as of yet, it only
 // applies to a subset of spec-defined Well-Known Symbols.
-#define WELL_KNOWN_SYMBOL_LIST(V) \
-  V(is_concat_spreadable_symbol, Symbol.isConcatSpreadable)
+#define WELL_KNOWN_SYMBOL_LIST(V)                           \
+  V(is_concat_spreadable_symbol, Symbol.isConcatSpreadable) \
+  V(to_string_tag_symbol, Symbol.toStringTag)
 
 // Heap roots that are known to be immortal immovable, for which we can safely
 // skip write barriers. This list is not complete and has omissions.
 #define IMMORTAL_IMMOVABLE_ROOT_LIST(V) \
   V(ByteArrayMap)                       \
   V(BytecodeArrayMap)                   \
   V(FreeSpaceMap)                       \
   V(OnePointerFillerMap)                \
   V(TwoPointerFillerMap)                \
   V(UndefinedValue)                     \
@@ skipping 2341 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_