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

src/isolate.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/isolate.h"
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
@@ skipping 2641 matching lines @@
     // @@isConcatSpreadable property on Array.prototype or Object.prototype
     // hence the reverse implication doesn't hold.
     DCHECK(is_is_concat_spreadable_set);
     return false;
   }
 #endif  // DEBUG
 
   return !is_is_concat_spreadable_set;
 }
 
+bool Isolate::IsIsConcatSpreadableLookupChainIntact(JSReceiver* receiver) {
+  if (!IsIsConcatSpreadableLookupChainIntact()) return false;
+  return !receiver->HasProxyInPrototype(this);
+}
+
 void Isolate::UpdateArrayProtectorOnSetElement(Handle<JSObject> object) {
   DisallowHeapAllocation no_gc;
   if (!object->map()->is_prototype_map()) return;
   if (!IsFastArrayConstructorPrototypeChainIntact()) return;
   if (!IsArrayOrObjectPrototype(*object)) return;
   PropertyCell::SetValueWithInvalidation(
       factory()->array_protector(),
       handle(Smi::FromInt(kArrayProtectorInvalid), this));
 }
 
@@ skipping 415 matching lines @@
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8