Use constexpr TaskTraits constructor in chrome.

chrome/browser/ui/webui/chromeos/login/encryption_migration_screen_handler.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/ui/webui/chromeos/login/encryption_migration_screen_handler.h"
 
 #include <cmath>
 #include <string>
 #include <utility>
 
@@ skipping 249 matching lines @@
 
   // We should block power save during migration.
   if (state == UIState::MIGRATING)
     StartBlockingPowerSave();
   else
     StopBlockingPowerSave();
 }
 
 void EncryptionMigrationScreenHandler::CheckAvailableStorage() {
   base::PostTaskWithTraitsAndReplyWithResult(
-      FROM_HERE,
-      base::TaskTraits().MayBlock().WithPriority(
-          base::TaskPriority::USER_VISIBLE),
+      FROM_HERE, {base::MayBlock(), base::TaskPriority::USER_VISIBLE},
       base::Bind(&base::SysInfo::AmountOfFreeDiskSpace,
                  base::FilePath(kCheckStoragePath)),
       base::Bind(&EncryptionMigrationScreenHandler::OnGetAvailableStorage,
                  weak_ptr_factory_.GetWeakPtr()));
 }
 
 void EncryptionMigrationScreenHandler::OnGetAvailableStorage(int64_t size) {
   if (size >= kMinimumAvailableStorage || IsTestingUI()) {
     if (should_resume_) {
       RecordFirstScreen(FirstScreen::FIRST_SCREEN_RESUME);
@@ skipping 147 matching lines @@
       break;
   }
 }
 
 void EncryptionMigrationScreenHandler::OnMigrationRequested(bool success) {
   LOG_IF(ERROR, !success) << "Requesting MigrateToDircrypto failed.";
   UpdateUIState(UIState::MIGRATION_FAILED);
 }
 
 }  // namespace chromeos