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

[maniscalco, 2014/04/15 16:29:14]

How do you envision backups working with attachments?  Currently, each
GenericChangeProcessor has an AttachmentService which is responsible for
managing and providing access to that datatype's attachments.  Would
SyncBackupManager call out to each AttachmentService and ask it to make a backup
of the datatype's attachments?

[haitaol1, 2014/04/15 16:59:51]

Backup is only for local data. Does local model create attachment when sync is
disabled? If not, then there should be no attachments to back up.

On 2014/04/15 16:29:14, maniscalco wrote:

[maniscalco, 2014/04/15 17:21:19]

Model type code will not create attachments when sync is disabled.  I think I
understand, you're saying that this feature will only backup unsynced data?  If
that's right, can you update this class comment?  When I first read it, I
interpreted it as backing up the current sync db, which isn't what it's doing.

On 2014/04/15 16:59:51, haitaol1 wrote:

[haitaol1, 2014/04/15 18:11:20]

Done.

+// 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_