Use constexpr TaskTraits constructor in chrome.

chrome/browser/platform_util.cc

 // Copyright 2015 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/platform_util.h"
 
 #include "base/files/file.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/task_scheduler/post_task.h"
@@ skipping 43 matching lines @@
 }
 
 }  // namespace internal
 
 void OpenItem(Profile* profile,
               const base::FilePath& full_path,
               OpenItemType item_type,
               const OpenOperationCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   base::PostTaskWithTraits(FROM_HERE,
-                           base::TaskTraits().MayBlock().WithPriority(
-                               base::TaskPriority::BACKGROUND),
+                           {base::MayBlock(), base::TaskPriority::BACKGROUND},
                            base::BindOnce(&VerifyAndOpenItemOnBlockingThread,
                                           full_path, item_type, callback));
 }
 
 }  // namespace platform_util