Add integraton test for sync backup/rollback.

sync/test/fake_server/fake_server.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_FAKE_SERVER_H_
 #define SYNC_TEST_FAKE_SERVER_FAKE_SERVER_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 52 matching lines @@
   bool SetNewStoreBirthday(const std::string& store_birthday);
 
   // Puts the server in a state where it acts as if authentication has
   // succeeded.
   void SetAuthenticated();
 
   // Puts the server in a state where all commands will fail with an
   // authentication error.
   void SetUnauthenticated();
 
+  // Return |error_type| on next sync request.
+  void TriggerError(const sync_pb::SyncEnums::ErrorType& error_type);
+
   // Adds |observer| to FakeServer's observer list. This should be called
   // before the Profile associated with |observer| is connected to the server.
   void AddObserver(Observer* observer);
 
   // Removes |observer| from the FakeServer's observer list. This method
   // must be called if AddObserver was ever called with |observer|.
   void RemoveObserver(Observer* observer);
 
  private:
   typedef std::map<std::string, FakeServerEntity*> EntityMap;
@@ skipping 52 matching lines @@
   // authenticated.
   bool authenticated_;
 
   // All SyncEntity objects saved by the server. The key value is the entity's
   // id string.
   EntityMap entities_;
 
   // All Keystore keys known to the server.
   std::vector<std::string> keystore_keys_;
 
+  sync_pb::SyncEnums::ErrorType error_type_;
+
   // FakeServer's observers.
   ObserverList<Observer, true> observers_;
 };
 
 }  // namespace fake_server
 
 #endif  // SYNC_TEST_FAKE_SERVER_FAKE_SERVER_H_