Fix mandatory TaskTraits destination in Windows+is_chrome_branded builds

This is a precursor to
https://chromium-review.googlesource.com/c/chromium/src/+/1761362
which is making destination a mandatory trait.

@OWNERS: Please verify that these traits indeed intended to post
to the ThreadPool.

Bug: 968047
Change-Id: Ia7c9bb718325e5fac727421aa62b6e6034987d6e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1761363
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Auto-Submit: Gabriel Charette <gab@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#689077}

chrome/browser/google/google_update_win.cc

@@ -387,11 +387,11 @@ UpdateCheckDriver::UpdateCheckDriver(
     bool install_update_if_possible,
     gfx::AcceleratedWidget elevation_window,
     const base::WeakPtr<UpdateCheckDelegate>& delegate)
-    : task_runner_(
-          g_update_driver_task_runner
-              ? g_update_driver_task_runner
-              : base::CreateCOMSTATaskRunner(
-                    {base::MayBlock(), base::TaskPriority::USER_VISIBLE})),
+    : task_runner_(g_update_driver_task_runner
+                       ? g_update_driver_task_runner
+                       : base::CreateCOMSTATaskRunner(
+                             {base::ThreadPool(), base::MayBlock(),
+                              base::TaskPriority::USER_VISIBLE})),
       result_runner_(base::SequencedTaskRunnerHandle::Get()),
       locale_(locale),
       install_update_if_possible_(install_update_if_possible),

chrome/browser/ui/webui/help/version_updater_win.cc

@@ -41,7 +41,9 @@ void VersionUpdaterWin::OnUpdateCheckComplete(
     // Google Update says that no new version is available. Check to see if a
     // restart is needed for a previously-applied update to take effect.
     base::PostTaskAndReplyWithResult(
-        FROM_HERE, {base::MayBlock(), base::TaskPriority::USER_VISIBLE},
+        FROM_HERE,
+        {base::ThreadPool(), base::MayBlock(),
+         base::TaskPriority::USER_VISIBLE},
         base::Bind(&upgrade_util::IsUpdatePendingRestart),
         base::Bind(&VersionUpdaterWin::OnPendingRestartCheck,
                    weak_factory_.GetWeakPtr()));