Add sync manager classes for backup/rollback:

sync/internal_api/sync_backup_manager.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_INTERNAL_API_SYNC_BACKUP_MANAGER_H_
+#define SYNC_INTERNAL_API_SYNC_BACKUP_MANAGER_H_
+
+#include <set>
+
+#include "sync/internal_api/sync_rollback_manager_base.h"
+
+namespace syncer {
+
+// SyncBackupManager runs before user signs into sync to back up user's data

[Nicolas Zea, 2014/04/15 23:05:51]

nit: into -> in to

[haitaol1, 2014/04/16 21:52:36]

Done.

+// before sync starts. The data that's backed up can be used to restore user's
+// settings to pre-sync state.
+class SyncBackupManager : public SyncRollbackManagerBase {
+ public:
+  SyncBackupManager();
+  virtual ~SyncBackupManager();
+
+  // SyncManager implementation.
+  virtual void SaveChanges() OVERRIDE;
+
+  // DirectoryChangeDelegate implementation.
+  virtual ModelTypeSet HandleTransactionEndingChangeEvent(
+      const syncable::ImmutableWriteTransactionInfo& write_transaction_info,
+      syncable::BaseTransaction* trans) OVERRIDE;
+
+ private:
+  // Replaces local IDs with server IDs and clear unsynced bit of modified
+  // entries.
+  void NormalizeEntries();
+
+  // Handles of unsynced entries caused by local model changes.
+  std::set<int64> unsynced_;
+
+  // True if NormalizeEntries() is being called.
+  bool in_normalization_;
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_INTERNAL_API_SYNC_BACKUP_MANAGER_H_