[builtins] take slow path in IsConcatSpreadable if proxy in prototype

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index 556082edf330bbd13f5e7a9b1ffea033e68d61e6..e17683ce47e572dc70b753446057404a8a92bbde 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -1183,7 +1183,7 @@ bool IterateElements(Isolate* isolate, Handle<JSReceiver> receiver,
 static Maybe<bool> IsConcatSpreadable(Isolate* isolate, Handle<Object> obj) {
   HandleScope handle_scope(isolate);
   if (!obj->IsJSReceiver()) return Just(false);
-  if (!isolate->IsIsConcatSpreadableLookupChainIntact()) {
+  if (!isolate->IsIsConcatSpreadableLookupChainIntact(JSReceiver::cast(*obj))) {
     // Slow path if @@isConcatSpreadable has been used.
     Handle<Symbol> key(isolate->factory()->is_concat_spreadable_symbol());
     Handle<Object> value;