Use constexpr TaskTraits constructor in chrome.

chrome/browser/chromeos/drive/fileapi/fileapi_worker.cc

 // 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.
 
 #include "chrome/browser/chromeos/drive/fileapi/fileapi_worker.h"
 
 #include <stddef.h>
 #include <utility>
 
 #include "base/files/file_path.h"
@@ skipping 167 matching lines @@
     file_flags &= ~(base::File::FLAG_CREATE |
                     base::File::FLAG_OPEN_ALWAYS);
     file_flags |= base::File::FLAG_OPEN;
   } else if (file_flags & base::File::FLAG_CREATE_ALWAYS) {
     file_flags &= ~base::File::FLAG_CREATE_ALWAYS;
     file_flags |= base::File::FLAG_OPEN_TRUNCATED;
   }
 
   // Cache file prepared for modification is available. Open it locally.
   base::PostTaskWithTraitsAndReplyWithResult(
-      FROM_HERE, base::TaskTraits().MayBlock(),
+      FROM_HERE, {base::MayBlock()},
       base::Bind(&OpenFile, local_path, file_flags),
       base::Bind(&RunOpenFileCallback, callback, close_callback));
 }
 
 }  // namespace
 
 FileSystemInterface* GetFileSystemFromUrl(const storage::FileSystemURL& url) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   Profile* profile = util::ExtractProfileFromPath(url.path());
@@ skipping 160 matching lines @@
                const StatusCallback& callback,
                FileSystemInterface* file_system) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   file_system->TouchFile(file_path, last_access_time, last_modified_time,
                          base::Bind(&RunStatusCallbackByFileError, callback));
 
 }
 
 }  // namespace fileapi_internal
 }  // namespace drive