[SyncFS] Make DumpFiles async

chrome/browser/sync_file_system/drive_backend/sync_engine.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_SYNC_ENGINE_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_SYNC_ENGINE_H_
 
 #include <set>
 #include <string>
 
@@ skipping 73 matching lines @@
       const GURL& origin,
       UninstallFlag flag,
       const SyncStatusCallback& callback) OVERRIDE;
   virtual void ProcessRemoteChange(const SyncFileCallback& callback) OVERRIDE;
   virtual void SetRemoteChangeProcessor(
       RemoteChangeProcessor* processor) OVERRIDE;
   virtual LocalChangeProcessor* GetLocalChangeProcessor() OVERRIDE;
   virtual bool IsConflicting(const fileapi::FileSystemURL& url) OVERRIDE;
   virtual RemoteServiceState GetCurrentState() const OVERRIDE;
   virtual void GetOriginStatusMap(OriginStatusMap* status_map) OVERRIDE;
-  virtual scoped_ptr<base::ListValue> DumpFiles(const GURL& origin) OVERRIDE;
+  virtual void DumpFiles(const GURL& origin,
+                         const ListCallback& callback) OVERRIDE;
   virtual scoped_ptr<base::ListValue> DumpDatabase() OVERRIDE;
   virtual void SetSyncEnabled(bool enabled) OVERRIDE;
   virtual SyncStatusCode SetDefaultConflictResolutionPolicy(
       ConflictResolutionPolicy policy) OVERRIDE;
   virtual SyncStatusCode SetConflictResolutionPolicy(
       const GURL& origin,
       ConflictResolutionPolicy policy) OVERRIDE;
   virtual ConflictResolutionPolicy GetDefaultConflictResolutionPolicy()
       const OVERRIDE;
   virtual ConflictResolutionPolicy GetConflictResolutionPolicy(
@@ skipping 77 matching lines @@
   scoped_refptr<base::SequencedTaskRunner> worker_task_runner_;
 
   base::WeakPtrFactory<SyncEngine> weak_ptr_factory_;
   DISALLOW_COPY_AND_ASSIGN(SyncEngine);
 };
 
 }  // namespace drive_backend
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_SYNC_ENGINE_H_