Use constexpr TaskTraits constructor in chrome.

chrome/browser/ui/app_list/arc/arc_default_app_list.cc

Index: chrome/browser/ui/app_list/arc/arc_default_app_list.cc
diff --git a/chrome/browser/ui/app_list/arc/arc_default_app_list.cc b/chrome/browser/ui/app_list/arc/arc_default_app_list.cc
index 78d3f9a38a4cb7f896125438c1cf6c0213624f48..44c85fce723d548a1afa9feab6dde75d0a6e09e9 100644
--- a/chrome/browser/ui/app_list/arc/arc_default_app_list.cc
+++ b/chrome/browser/ui/app_list/arc/arc_default_app_list.cc
@@ -129,8 +129,7 @@ ArcDefaultAppList::ArcDefaultAppList(Delegate* delegate,
 
   // Once ready OnAppsReady is called.
   base::PostTaskWithTraitsAndReplyWithResult(
-      FROM_HERE, base::TaskTraits().MayBlock().WithPriority(
-                     base::TaskPriority::BACKGROUND),
+      FROM_HERE, {base::MayBlock(), base::TaskPriority::BACKGROUND},
       base::Bind(&ReadAppsFromFileThread),
       base::Bind(&ArcDefaultAppList::OnAppsReady,
                  weak_ptr_factory_.GetWeakPtr()));