Use constexpr TaskTraits constructor in chrome.

chrome/browser/feature_engagement_tracker/feature_engagement_tracker_factory.cc

 // Copyright 2017 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/feature_engagement_tracker/feature_engagement_tracker_factory.h"
 
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/singleton.h"
 #include "base/sequenced_task_runner.h"
@@ skipping 25 matching lines @@
           BrowserContextDependencyManager::GetInstance()) {}
 
 FeatureEngagementTrackerFactory::~FeatureEngagementTrackerFactory() = default;
 
 KeyedService* FeatureEngagementTrackerFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
   Profile* profile = Profile::FromBrowserContext(context);
 
   scoped_refptr<base::SequencedTaskRunner> background_task_runner =
       base::CreateSequencedTaskRunnerWithTraits(
-          base::TaskTraits().MayBlock().WithPriority(
-              base::TaskPriority::BACKGROUND));
+          {base::MayBlock(), base::TaskPriority::BACKGROUND});
 
   base::FilePath storage_dir = profile->GetPath().Append(
       chrome::kFeatureEngagementTrackerStorageDirname);
 
   return feature_engagement_tracker::FeatureEngagementTracker::Create(
       storage_dir, background_task_runner);
 }
 
 content::BrowserContext*
 FeatureEngagementTrackerFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextRedirectedInIncognito(context);
 }