The ArrayConcat builtin didn't respect @@isConcatSp

src/runtime/runtime-array.cc

Index: src/runtime/runtime-array.cc
diff --git a/src/runtime/runtime-array.cc b/src/runtime/runtime-array.cc
index af2d4c54813104a5e9566293951e9c488822b9fd..9cdf9237e0c52ace1caa54d88d082ed22966d360 100644
--- a/src/runtime/runtime-array.cc
+++ b/src/runtime/runtime-array.cc
@@ -726,24 +726,6 @@ static bool IterateElements(Isolate* isolate, Handle<JSObject> receiver,
 }
 
 
-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.