[SyncFS] Make DumpFiles async

chrome/browser/sync_file_system/mock_remote_file_sync_service.cc

Index: chrome/browser/sync_file_system/mock_remote_file_sync_service.cc
diff --git a/chrome/browser/sync_file_system/mock_remote_file_sync_service.cc b/chrome/browser/sync_file_system/mock_remote_file_sync_service.cc
index a6f933bebd92032a1ed16ad98a47043629f3630b..8444a41dbd20c2fa51854422eed5ffd7c398a94d 100644
--- a/chrome/browser/sync_file_system/mock_remote_file_sync_service.cc
+++ b/chrome/browser/sync_file_system/mock_remote_file_sync_service.cc
@@ -54,9 +54,9 @@ MockRemoteFileSyncService::MockRemoteFileSyncService()
 MockRemoteFileSyncService::~MockRemoteFileSyncService() {
 }
 
-scoped_ptr<base::ListValue> MockRemoteFileSyncService::DumpFiles(
-    const GURL& origin) {
-  return scoped_ptr<base::ListValue>();
+void MockRemoteFileSyncService::DumpFiles(const GURL& origin,
+                                          const ListCallback& callback) {
+  callback.Run(scoped_ptr<base::ListValue>());
 }
 
 scoped_ptr<base::ListValue> MockRemoteFileSyncService::DumpDatabase() {