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

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index 444f9a308b4297012940a1aa1829593a00695146..8395b31fc9787566b87100d7b0f924b9e74cff3a 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -1186,11 +1186,17 @@ bool IsConcatSpreadable(Isolate* isolate, Handle<Object> obj) {
   HandleScope handle_scope(isolate);
   if (!obj->IsSpecObject()) return false;
   if (FLAG_harmony_concat_spreadable) {
+    // [[Get]] @@isConcatSpreadable from object. If an access check failed,
+    // ignore the resulting value and use the default behaviour. Otherwise,
+    // use the boolean value of the result.
     Handle<Symbol> key(isolate->factory()->is_concat_spreadable_symbol());
     Handle<Object> value;
+    bool access_check_failed;
+    LookupIterator it(obj, key, LookupIterator::DEFAULT);
     MaybeHandle<Object> maybeValue =
-        i::Runtime::GetObjectProperty(isolate, obj, key);
-    if (maybeValue.ToHandle(&value) && !value->IsUndefined()) {
+        Object::GetPropertyEx(&it, access_check_failed);
+    if (!access_check_failed && maybeValue.ToHandle(&value) &&
+        !value->IsUndefined()) {
       return value->BooleanValue();
     }
   }