Use constexpr TaskTraits constructor in chrome.

chrome/browser/media_galleries/chromeos/mtp_device_delegate_impl_chromeos.cc

 // Copyright (c) 2012 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/media_galleries/chromeos/mtp_device_delegate_impl_chromeos.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <stddef.h>
 
@@ skipping 333 matching lines @@
 // Closes |file_descriptor| on file thread.
 void CloseFileDescriptor(const int file_descriptor) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::FILE);
 
   IGNORE_EINTR(close(file_descriptor));
 }
 
 // Deletes a temporary file |file_path|.
 void DeleteTemporaryFile(const base::FilePath& file_path) {
   base::PostTaskWithTraits(FROM_HERE,
-                           base::TaskTraits().MayBlock().WithPriority(
-                               base::TaskPriority::BACKGROUND),
+                           {base::MayBlock(), base::TaskPriority::BACKGROUND},
                            base::Bind(base::IgnoreResult(base::DeleteFile),
                                       file_path, false /* not recursive*/));
 }
 
 // A fake callback to be passed as CopyFileProgressCallback.
 void FakeCopyFileProgressCallback(int64_t size) {}
 
 }  // namespace
 
 MTPDeviceDelegateImplLinux::PendingTaskInfo::PendingTaskInfo(
@@ skipping 1528 matching lines @@
   }
 }
 
 void CreateMTPDeviceAsyncDelegate(
     const std::string& device_location,
     const bool read_only,
     const CreateMTPDeviceAsyncDelegateCallback& callback) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
   callback.Run(new MTPDeviceDelegateImplLinux(device_location, read_only));
 }