Use constexpr TaskTraits constructor in extensions.

extensions/browser/updater/update_install_shim.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 "extensions/browser/updater/update_install_shim.h"
 
 #include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
@@ skipping 62 matching lines @@
 bool UpdateInstallShim::Uninstall() {
   NOTREACHED();
   return false;
 }
 
 UpdateInstallShim::~UpdateInstallShim() {}
 
 void UpdateInstallShim::RunCallbackOnUIThread(const base::FilePath& temp_dir) {
   if (callback_.is_null()) {
     base::PostTaskWithTraits(FROM_HERE,
-                             base::TaskTraits().MayBlock().WithPriority(
-                                 base::TaskPriority::BACKGROUND),
+                             {base::MayBlock(), base::TaskPriority::BACKGROUND},
                              base::Bind(base::IgnoreResult(&base::DeleteFile),
                                         temp_dir, true /*recursive */));
     return;
   }
   callback_.Run(extension_id_, temp_dir);
 }
 
 }  // namespace extensions