Use constexpr TaskTraits constructor in chrome.

chrome/browser/chromeos/system_logs/touch_log_source_x11.cc

 // Copyright (c) 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/chromeos/system_logs/touch_log_source.h"
 
 #include <stddef.h>
 
 #include "ash/touch/touch_hud_debug.h"
 #include "base/bind.h"
@@ skipping 44 matching lines @@
 
 }  // namespace
 
 namespace system_logs {
 
 void TouchLogSource::Fetch(const SysLogsSourceCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK(!callback.is_null());
 
   SystemLogsResponse* response = new SystemLogsResponse;
-  base::PostTaskWithTraitsAndReply(FROM_HERE,
-                                   base::TaskTraits().MayBlock().WithPriority(
-                                       base::TaskPriority::BACKGROUND),
-                                   base::Bind(&GetTouchLogsX11, response),
-                                   base::Bind(callback, base::Owned(response)));
+  base::PostTaskWithTraitsAndReply(
+      FROM_HERE, {base::MayBlock(), base::TaskPriority::BACKGROUND},
+      base::Bind(&GetTouchLogsX11, response),
+      base::Bind(callback, base::Owned(response)));
 }
 
 }  // namespace system_logs