Use constexpr TaskTraits constructor in chrome.

chrome/browser/extensions/api/developer_private/developer_private_api.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/extensions/api/developer_private/developer_private_api.h"
 
 #include <stddef.h>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 1292 matching lines @@
   // the extension's directory. If it tries to, abort.
   base::FilePath path_suffix =
       base::FilePath::FromUTF8Unsafe(properties.path_suffix);
   if (path_suffix.empty() || path_suffix.ReferencesParent())
     return RespondNow(Error(kInvalidPathError));
 
   if (properties.path_suffix == kManifestFile && !properties.manifest_key)
     return RespondNow(Error(kManifestKeyIsRequiredError));
 
   base::PostTaskWithTraitsAndReplyWithResult(
-      FROM_HERE, base::TaskTraits().MayBlock().WithPriority(
-                     base::TaskPriority::USER_VISIBLE),
+      FROM_HERE, {base::MayBlock(), base::TaskPriority::USER_VISIBLE},
       base::Bind(&ReadFileToString, extension->path().Append(path_suffix)),
       base::Bind(&DeveloperPrivateRequestFileSourceFunction::Finish, this));
 
   return RespondLater();
 }
 
 void DeveloperPrivateRequestFileSourceFunction::Finish(
     const std::string& file_contents) {
   const developer::RequestFileSourceProperties& properties =
       params_->properties;
@@ skipping 252 matching lines @@
         update.extension_id, update.command_name, *update.keybinding);
   }
 
   return RespondNow(NoArguments());
 }
 
 
 }  // namespace api
 
 }  // namespace extensions