[SyncFS] Implement SyncEngineInitializer

chrome/browser/sync_file_system/drive_backend/metadata_database.h

 // Copyright 2013 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 CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_METADATA_DATABASE_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_METADATA_DATABASE_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 105 matching lines @@
       void(SyncStatusCode status, scoped_ptr<MetadataDatabase> instance)>
       CreateCallback;
 
   // The entry point of the MetadataDatabase for production code.
   static void Create(base::SequencedTaskRunner* task_runner,
                      const base::FilePath& database_path,
                      const CreateCallback& callback);
   ~MetadataDatabase();
 
   int64 GetLargestChangeID() const;
-
+  int64 GetSyncRootTrackerID() const;
   bool HasSyncRoot() const;
 
   // Populates empty database with initial data.
   // Adds a file metadata and a file tracker for |sync_root_folder|, and adds
   // file metadata and file trackers for each |app_root_folders|.
   // Newly added tracker for |sync_root_folder| is active and non-dirty.
   // Newly added trackers for |app_root_folders| are inactive and non-dirty.
   // Trackers for |app_root_folders| are not yet registered as app-roots, but
   // are ready to register.
   void PopulateInitialData(
@@ skipping 190 matching lines @@
 
   base::WeakPtrFactory<MetadataDatabase> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MetadataDatabase);
 };
 
 }  // namespace drive_backend
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_METADATA_DATABASE_H_