Use task runner in version_updater_win.cc.

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

Index: chrome/browser/ui/webui/help/version_updater_win.cc
diff --git a/chrome/browser/ui/webui/help/version_updater_win.cc b/chrome/browser/ui/webui/help/version_updater_win.cc
index 43bcd5945b4b3fd9a608a9030900a6a7785775b0..88e3bf3f62e6408dc79d6e687f7c7ae35a1d7e72 100644
--- a/chrome/browser/ui/webui/help/version_updater_win.cc
+++ b/chrome/browser/ui/webui/help/version_updater_win.cc
@@ -5,14 +5,12 @@
 #include "chrome/browser/ui/webui/help/version_updater_win.h"
 
 #include "base/memory/weak_ptr.h"
-#include "base/task_runner_util.h"
-#include "base/threading/sequenced_worker_pool.h"
+#include "base/task_scheduler/post_task.h"
 #include "base/win/win_util.h"
 #include "base/win/windows_version.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/first_run/upgrade_util.h"
 #include "chrome/grit/generated_resources.h"
-#include "content/public/browser/browser_thread.h"
 #include "content/public/browser/web_contents.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_tree_host.h"
@@ -46,47 +44,37 @@ void VersionUpdaterWin::CheckForUpdate(const StatusCallback& callback,
 
 void VersionUpdaterWin::OnUpdateCheckComplete(
     const base::string16& new_version) {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   Status status = CHECKING;
   if (new_version.empty()) {
     // 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.
-    if (base::PostTaskAndReplyWithResult(
-            content::BrowserThread::GetBlockingPool(),
-            FROM_HERE,
-            base::Bind(&upgrade_util::IsUpdatePendingRestart),
-            base::Bind(&VersionUpdaterWin::OnPendingRestartCheck,
-                       weak_factory_.GetWeakPtr()))) {
-      // Early exit since callback_ will be Run in OnPendingRestartCheck.
-      return;
-    }
-    // Failure to post the task means that Chrome is shutting down. A pending
-    // update (if there is one) will be applied as Chrome exits, so tell the
-    // caller that it is up to date in either case.
-    status = UPDATED;
-  } else {
-    // Notify the caller that the update is now beginning and initiate it.
-    status = UPDATING;
-    BeginUpdateCheckOnFileThread(true /* install_update_if_possible */);
+    base::PostTaskWithTraitsAndReplyWithResult(
+        FROM_HERE, {base::MayBlock(), base::TaskPriority::USER_VISIBLE},
+        base::Bind(&upgrade_util::IsUpdatePendingRestart),
+        base::Bind(&VersionUpdaterWin::OnPendingRestartCheck,
+                   weak_factory_.GetWeakPtr()));
+    // Early exit since callback_ will be Run in OnPendingRestartCheck.
+    return;
   }
+
+  // Notify the caller that the update is now beginning and initiate it.
+  status = UPDATING;
+  BeginUpdateCheckOnFileThread(true /* install_update_if_possible */);
   callback_.Run(status, 0, std::string(), 0, base::string16());
 }
 
 void VersionUpdaterWin::OnUpgradeProgress(int progress,
                                           const base::string16& new_version) {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   callback_.Run(UPDATING, progress, std::string(), 0, base::string16());
 }
 
 void VersionUpdaterWin::OnUpgradeComplete(const base::string16& new_version) {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   callback_.Run(NEARLY_UPDATED, 0, std::string(), 0, base::string16());
 }
 
 void VersionUpdaterWin::OnError(GoogleUpdateErrorCode error_code,
                                 const base::string16& html_error_message,
                                 const base::string16& new_version) {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);

[gab, 2017/07/11 23:40:15]

It's fine to keep these (the UI thread isn't going away at this time)

[calamity, 2017/07/12 07:11:40]

Done.

   base::string16 message;
   Status status = FAILED;
 
@@ -118,8 +106,8 @@ void VersionUpdaterWin::BeginUpdateCheckOnFileThread(
     bool install_update_if_possible) {
   // Disconnect from any previous attempts to avoid redundant callbacks.
   weak_factory_.InvalidateWeakPtrs();
-  BeginUpdateCheck(content::BrowserThread::GetTaskRunnerForThread(
-                       content::BrowserThread::FILE),
+  BeginUpdateCheck(base::CreateSingleThreadTaskRunnerWithTraits(

[gab, 2017/07/11 23:40:15]

Have the leaves of this call obtain the task runner they need directly instead
of having it injected :
https://chromium.googlesource.com/chromium/src/+/lkcr/docs/threading_and_task...

[calamity, 2017/07/12 07:11:40]

I gave this a shot. The latest patchset shows my attempt, but the unittests
fail, saying the expected method never gets called. Any suggestions or insights?

Thanks.

+                       {base::MayBlock(), base::TaskPriority::USER_VISIBLE}),
                    g_browser_process->GetApplicationLocale(),
                    install_update_if_possible, owner_widget_,
                    weak_factory_.GetWeakPtr());