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

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index c04488240d8d1d6af1f4992514747a9231c4f859..4bda6883693c17d85bac6ffe1488991c824cde0a 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1211,6 +1211,11 @@ class Object {
   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,