Make client tag IDs consistent in sync fake server

sync/test/fake_server/unique_client_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 SYNC_TEST_FAKE_SERVER_UNIQUE_CLIENT_ENTITY_H_
 #define SYNC_TEST_FAKE_SERVER_UNIQUE_CLIENT_ENTITY_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 10 matching lines @@
 
   // Factory function for UniqueClientEntity.
   static FakeServerEntity* CreateNew(const sync_pb::SyncEntity& client_entity);
 
   // Factory function for creating a new version of an existing
   // UniqueClientEntity.
   static FakeServerEntity* CreateUpdatedVersion(
       const sync_pb::SyncEntity& client_entity,
       FakeServerEntity* current_server_entity);
 
+  // Derives an ID from a unique client tagged entity.
+  static std::string EffectiveIdForClientTaggedEntity(
+      const sync_pb::SyncEntity& entity);
+
   // FakeServerEntity implementation.
   virtual std::string GetParentId() const OVERRIDE;
   virtual sync_pb::SyncEntity* SerializeAsProto() OVERRIDE;
   virtual bool IsDeleted() const OVERRIDE;
   virtual bool IsFolder() const OVERRIDE;
 
  private:
   UniqueClientEntity(const std::string& id,
                      const syncer::ModelType& model_type,
                      int64 version,
                      const std::string& name,
                      const std::string& client_defined_unique_tag,
                      const sync_pb::EntitySpecifics& specifics,
                      int64 creation_time,
                      int64 last_modified_time);
 
   // These member values have equivalent fields in SyncEntity.
   std::string client_defined_unique_tag_;
   sync_pb::EntitySpecifics specifics_;
   int64 creation_time_;
   int64 last_modified_time_;
 };
 
 }  // namespace fake_server
 
 #endif  // SYNC_TEST_FAKE_SERVER_UNIQUE_CLIENT_ENTITY_H_