[runtime] Avoid @@isConcatSpreadable lookup for fast path Array.prototype.concat

src/isolate-inl.h

 // Copyright 2015 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.
 
 #ifndef V8_ISOLATE_INL_H_
 #define V8_ISOLATE_INL_H_
 
 #include "src/isolate.h"
 #include "src/objects-inl.h"
 
@@ skipping 97 matching lines @@
   // what the protector stands for:
   // - You'd need to traverse the heap to check that no Array instance has
   //   a constructor property
   // - To check that Array[Symbol.species] == Array, JS code has to execute,
   //   but JS cannot be invoked in callstack overflow situations
   // All that could be checked reliably is that
   // Array.prototype.constructor == Array. Given that limitation, no check is
   // done here. In place, there are mjsunit tests harmony/array-species* which
   // ensure that behavior is correct in various invalid protector cases.
 
-  PropertyCell* species_cell = heap()->species_protector();
+  Cell* species_cell = heap()->species_protector();
   return species_cell->value()->IsSmi() &&
          Smi::cast(species_cell->value())->value() == kArrayProtectorValid;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ISOLATE_INL_H_