Revert "Fix misoptimization of 'is' test"

runtime/vm/optimizer.h

-// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-#ifndef RUNTIME_VM_OPTIMIZER_H_
-#define RUNTIME_VM_OPTIMIZER_H_
-
-#include "vm/globals.h"
-
-#include "vm/growable_array.h"
-
-namespace dart {
-
-class Optimizer {
- public:
-  // Tries to add cid tests to 'results' so that no deoptimization is
-  // necessary for common number-related type tests.  Unconditionally adds an
-  // entry for the Smi type to the start of the array.
-  // TODO(srdjan): Do also for other than numeric types.
-  static bool SpecializeTestCidsForNumericTypes(
-      ZoneGrowableArray<intptr_t>* results,
-      const AbstractType& type);
-};
-
-}  // namespace dart
-
-#endif  // RUNTIME_VM_OPTIMIZER_H_