[SyncFS] Migrate ServiceMetadata from MDDB to MDDBIndex.

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 405 matching lines @@
                                   leveldb::WriteBatch* batch);
 
   void DetachFromSequence();
 
   scoped_refptr<base::SequencedTaskRunner> worker_task_runner_;
   scoped_refptr<base::SequencedTaskRunner> file_task_runner_;
   base::FilePath database_path_;
   leveldb::Env* env_override_;
   scoped_ptr<leveldb::DB> db_;
 
-  scoped_ptr<ServiceMetadata> service_metadata_;
   int64 largest_known_change_id_;
 
   scoped_ptr<MetadataDatabaseIndexInterface> index_;
 
   base::WeakPtrFactory<MetadataDatabase> weak_ptr_factory_;
 
   base::SequenceChecker worker_sequence_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(MetadataDatabase);
 };
 
 }  // namespace drive_backend
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_METADATA_DATABASE_H_