Merge duplicate code in invalidation helper.

components/sync_driver/invalidation_helper.h

Index: components/sync_driver/invalidation_helper.h
diff --git a/components/sync_driver/invalidation_helper.h b/components/sync_driver/invalidation_helper.h
deleted file mode 100644
index fdde374a989fbe3059a8706ea7571ee60406ab41..0000000000000000000000000000000000000000
--- a/components/sync_driver/invalidation_helper.h
+++ /dev/null
@@ -1,20 +0,0 @@
-// Copyright 2014 The Chromium 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 COMPONENTS_SYNC_DRIVER_INVALIDATION_HELPER_H_
-#define COMPONENTS_SYNC_DRIVER_INVALIDATION_HELPER_H_
-
-#include "components/invalidation/public/invalidation_util.h"
-#include "google/cacheinvalidation/include/types.h"
-#include "sync/internal_api/public/base/model_type.h"
-
-namespace syncer {
-
-bool RealModelTypeToObjectId(ModelType model_type,
-                             invalidation::ObjectId* object_id);
-
-ObjectIdSet ModelTypeSetToObjectIdSet(ModelTypeSet model_types);
-}
-
-#endif  // COMPONENTS_SYNC_DRIVER_INVALIDATION_HELPER_H_