The ArrayConcat builtin didn't respect @@isConcatSp

src/runtime/runtime-array.cc

 // Copyright 2014 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/v8.h"
 
 #include "src/arguments.h"
 #include "src/elements.h"
 #include "src/messages.h"
 #include "src/runtime/runtime-utils.h"
@@ skipping 708 matching lines @@
         visitor->visit(index, element);
       }
       break;
     }
   }
   visitor->increase_index_offset(length);
   return true;
 }
 
 
-static bool IsConcatSpreadable(Isolate* isolate, Handle<Object> obj) {
-  HandleScope handle_scope(isolate);
-  if (!obj->IsSpecObject()) return false;
-  if (FLAG_harmony_concat_spreadable) {
-    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)) {
-      if (!value->IsUndefined()) {
-        return value->BooleanValue();
-      }
-    }
-  }
-  return obj->IsJSArray();
-}
-
-
 /**
  * Array::concat implementation.
  * See ECMAScript 262, 15.4.4.4.
  * TODO(581): Fix non-compliance for very large concatenations and update to
  * following the ECMAScript 5 specification.
  */
 RUNTIME_FUNCTION(Runtime_ArrayConcat) {
   HandleScope handle_scope(isolate);
   DCHECK(args.length() == 1);
 
@@ skipping 563 matching lines @@
 
 RUNTIME_FUNCTION(Runtime_FastOneByteArrayJoin) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 2);
   // Returning undefined means that this fast path fails and one has to resort
   // to a slow path.
   return isolate->heap()->undefined_value();
 }
 }  // namespace internal
 }  // namespace v8