[Sync] Fixing easy lint violations.

components/sync/test/fake_server/tombstone_entity.h

 // 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_TEST_FAKE_SERVER_TOMBSTONE_ENTITY_H_
 #define COMPONENTS_SYNC_TEST_FAKE_SERVER_TOMBSTONE_ENTITY_H_
 
+#include <memory>
 #include <string>
 
 #include "components/sync/base/model_type.h"
 #include "components/sync/protocol/sync.pb.h"
 #include "components/sync/test/fake_server/fake_server_entity.h"
 
 namespace fake_server {
 
 // A Sync entity that represents a deleted item.
 class TombstoneEntity : public FakeServerEntity {
@@ skipping 13 matching lines @@
 
  private:
   TombstoneEntity(const std::string& id,
                   const std::string& client_defined_unique_tag,
                   const syncer::ModelType& model_type);
 };
 
 }  // namespace fake_server
 
 #endif  // COMPONENTS_SYNC_TEST_FAKE_SERVER_TOMBSTONE_ENTITY_H_