[SyncFS] Make DumpFiles async

chrome/browser/sync_file_system/sync_file_system_service.h

Index: chrome/browser/sync_file_system/sync_file_system_service.h
diff --git a/chrome/browser/sync_file_system/sync_file_system_service.h b/chrome/browser/sync_file_system/sync_file_system_service.h
index 8831beb9d5d97ecec15fbfe124bc94d4c8032e58..0561a28fbe64ef7be58f90270167dbc2969df6fe 100644
--- a/chrome/browser/sync_file_system/sync_file_system_service.h
+++ b/chrome/browser/sync_file_system/sync_file_system_service.h
@@ -48,7 +48,7 @@ class SyncFileSystemService
       public content::NotificationObserver,
       public base::SupportsWeakPtr<SyncFileSystemService> {
  public:
-  typedef base::Callback<void(const base::ListValue* files)> DumpFilesCallback;
+  typedef base::Callback<void(const base::ListValue&)> DumpFilesCallback;
 
   // KeyedService overrides.
   virtual void Shutdown() OVERRIDE;
@@ -103,6 +103,9 @@ class SyncFileSystemService
   void DidInitializeFileSystemForDump(const GURL& app_origin,
                                       const DumpFilesCallback& callback,
                                       SyncStatusCode status);
+  void DidDumpFiles(const GURL& app_origin,
+                    const DumpFilesCallback& callback,
+                    scoped_ptr<base::ListValue> files);
 
   // Overrides sync_enabled_ setting. This should be called only by tests.
   void SetSyncEnabledForTesting(bool enabled);