[SyncFileSystem] Stop referring to DriveFileSyncService from extension/

chrome/browser/sync_file_system/sync_file_system_service.h

 // Copyright (c) 2012 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_SYNC_FILE_SYSTEM_SERVICE_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_SYNC_FILE_SYSTEM_SERVICE_H_
 
 #include <set>
 #include <string>
 
@@ skipping 49 matching lines @@
   void GetFileSyncStatus(
       const fileapi::FileSystemURL& url,
       const SyncFileStatusCallback& callback);
 
   void AddSyncEventObserver(SyncEventObserver* observer);
   void RemoveSyncEventObserver(SyncEventObserver* observer);
 
   ConflictResolutionPolicy GetConflictResolutionPolicy() const;
   SyncStatusCode SetConflictResolutionPolicy(ConflictResolutionPolicy policy);
 
+  static std::string GetDefaultServiceName();
+
  private:
   friend class SyncFileSystemServiceFactory;
   friend class SyncFileSystemServiceTest;
   friend struct base::DefaultDeleter<SyncFileSystemService>;
 
   explicit SyncFileSystemService(Profile* profile);
   virtual ~SyncFileSystemService();
 
   void Initialize(scoped_ptr<LocalFileSyncService> local_file_service,
                   scoped_ptr<RemoteFileSyncService> remote_file_service);
@@ skipping 90 matching lines @@
   base::OneShotTimer<SyncFileSystemService> sync_retry_timer_;
 
   ObserverList<SyncEventObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncFileSystemService);
 };
 
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_SYNC_FILE_SYSTEM_SERVICE_H_