[SyncFS] Make DumpFiles async

chrome/browser/ui/webui/sync_file_system_internals/file_metadata_handler.cc

 // 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.
 
 #include "chrome/browser/ui/webui/sync_file_system_internals/file_metadata_handler.h"
 
 #include <map>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 54 matching lines @@
                                      weak_factory_.GetWeakPtr()));
 }
 
 void FileMetadataHandler::GetExtensions(const base::ListValue* args) {
   DCHECK(args);
   base::ListValue list;
   ExtensionStatusesHandler::GetExtensionStatusesAsDictionary(profile_, &list);
   web_ui()->CallJavascriptFunction("FileMetadata.onGetExtensions", list);
 }
 
-void FileMetadataHandler::DidGetFileMetadata(const base::ListValue* files) {
-  DCHECK(files);
-  web_ui()->CallJavascriptFunction("FileMetadata.onGetFileMetadata", *files);
+void FileMetadataHandler::DidGetFileMetadata(const base::ListValue& files) {
+  web_ui()->CallJavascriptFunction("FileMetadata.onGetFileMetadata", files);
 }
 
 }  // namespace syncfs_internals