Add sync manager classes for backup/rollback:

sync/internal_api/sync_backup_manager.h

Index: sync/internal_api/sync_backup_manager.h
diff --git a/sync/internal_api/sync_backup_manager.h b/sync/internal_api/sync_backup_manager.h
new file mode 100644
index 0000000000000000000000000000000000000000..aec2e6c0169c062607fcef1735976234661781b8
--- /dev/null
+++ b/sync/internal_api/sync_backup_manager.h
@@ -0,0 +1,43 @@
+// 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
+// into sync DB.
+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_