[SyncFS] Make routines using metadata database async

chrome/browser/sync_file_system/drive_backend/sync_worker.h

 // 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 CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_SYNC_WORKER_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_SYNC_WORKER_H_
 
 #include <set>
 #include <string>
 
@@ skipping 51 matching lines @@
 
   class Observer {
    public:
     virtual void OnPendingFileListUpdated(int item_count) = 0;
     virtual void OnFileStatusChanged(const fileapi::FileSystemURL& url,
                                      SyncFileStatus file_status,
                                      SyncAction sync_action,
                                      SyncDirection direction) = 0;
     virtual void UpdateServiceState(RemoteServiceState state,
                                     const std::string& description) = 0;
+    virtual void OnPromoteDemotedChanges(size_t num_trackers) = 0;
 
    protected:
     virtual ~Observer() {}
   };
 
   SyncWorker(const base::FilePath& base_dir,
              const base::WeakPtr<ExtensionServiceInterface>& extension_service,
              scoped_ptr<SyncEngineContext> sync_engine_context,
              leveldb::Env* env_override);
 
@@ skipping 16 matching lines @@
       const SyncStatusCallback& callback);
   void ProcessRemoteChange(const SyncFileCallback& callback);
   void SetRemoteChangeProcessor(
       RemoteChangeProcessorOnWorker* remote_change_processor_on_worker);
   RemoteServiceState GetCurrentState() const;
   void GetOriginStatusMap(
       const RemoteFileSyncService::StatusMapCallback& callback);
   scoped_ptr<base::ListValue> DumpFiles(const GURL& origin);
   scoped_ptr<base::ListValue> DumpDatabase();
   void SetSyncEnabled(bool enabled);
+  void PromoteDemotedChanges();
   SyncStatusCode SetDefaultConflictResolutionPolicy(
       ConflictResolutionPolicy policy);
   SyncStatusCode SetConflictResolutionPolicy(
       const GURL& origin,
       ConflictResolutionPolicy policy);
   ConflictResolutionPolicy GetDefaultConflictResolutionPolicy()
       const;
   ConflictResolutionPolicy GetConflictResolutionPolicy(
       const GURL& origin) const;
 
@@ skipping 73 matching lines @@
   ObserverList<Observer> observers_;
 
   base::WeakPtrFactory<SyncWorker> weak_ptr_factory_;
   DISALLOW_COPY_AND_ASSIGN(SyncWorker);
 };
 
 }  // namespace drive_backend
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_SYNC_WORKER_H_