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

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 120ca988431a99dde0471883cd51b172573e77d6..42de1fb17be2fc8aee34768971897795c6853bc3 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -1157,6 +1157,16 @@ bool Object::HasSpecificClassOf(String* name) {
 }
 
 
+MaybeHandle<Object> Object::GetProperty(LookupIterator* it,
+                                        LanguageMode language_mode) {
+  bool failedAccessCheck = false;
+  MaybeHandle<Object> result =
+      GetPropertyInternal(it, &failedAccessCheck, language_mode);
+  if (failedAccessCheck) return JSObject::GetPropertyWithFailedAccessCheck(it);
+  return result;
+}
+
+
 MaybeHandle<Object> Object::GetProperty(Handle<Object> object,
                                         Handle<Name> name,
                                         LanguageMode language_mode) {
@@ -1165,6 +1175,20 @@ MaybeHandle<Object> Object::GetProperty(Handle<Object> object,
 }
 
 
+MaybeHandle<Object> Object::GetPropertyOrFallbackValue(
+    Handle<Object> object, Handle<Name> name, Handle<Object> fallbackValue,
+    LanguageMode language_mode) {
+  LookupIterator it(object, name);
+  bool failedAccessCheck = false;
+  MaybeHandle<Object> result =
+      GetPropertyInternal(&it, &failedAccessCheck, language_mode);
+  if (V8_UNLIKELY(failedAccessCheck)) {
+    result = fallbackValue;
+  }
+  return result;
+}
+
+
 MaybeHandle<Object> Object::GetElement(Isolate* isolate, Handle<Object> object,
                                        uint32_t index,
                                        LanguageMode language_mode) {