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

src/builtins.cc

 // 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.
 
 #include "src/builtins.h"
 
 #include "src/api-arguments.h"
 #include "src/api-natives.h"
 #include "src/api.h"
 #include "src/base/ieee754.h"
@@ skipping 1165 matching lines @@
       UNREACHABLE();
       break;
   }
   visitor->increase_index_offset(length);
   return true;
 }
 
 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;
     MaybeHandle<Object> maybeValue =
         i::Runtime::GetObjectProperty(isolate, obj, key);
     if (!maybeValue.ToHandle(&value)) return Nothing<bool>();
     if (!value->IsUndefined(isolate)) return Just(value->BooleanValue());
   }
   return Object::IsArray(obj);
 }
@@ skipping 5540 matching lines @@
 BUILTIN_LIST_H(DEFINE_BUILTIN_ACCESSOR_H)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 #undef DEFINE_BUILTIN_ACCESSOR_T
 #undef DEFINE_BUILTIN_ACCESSOR_S
 #undef DEFINE_BUILTIN_ACCESSOR_H
 
 }  // namespace internal
 }  // namespace v8