Use TaskScheduler instead of blocking pool in supervised_user_creation_controller_new.cc.

The blocking pool is being deprecated in favor of TaskScheduler.

BUG=667892
R=alemate@chromium.org

Review-Url: https://codereview.chromium.org/2841633003
Cr-Commit-Position: refs/heads/master@{#466859}

chrome/browser/chromeos/login/supervised/supervised_user_creation_controller_new.cc

@@ -13,7 +13,7 @@
 #include "base/strings/string_util.h"
 #include "base/sys_info.h"
 #include "base/task_runner_util.h"
-#include "base/threading/sequenced_worker_pool.h"
+#include "base/task_scheduler/post_task.h"
 #include "base/values.h"
 #include "chrome/browser/chromeos/login/supervised/supervised_user_authentication.h"
 #include "chrome/browser/chromeos/login/supervised/supervised_user_constants.h"
@@ -31,7 +31,6 @@
 #include "components/signin/core/account_id/account_id.h"
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_manager.h"
-#include "content/public/browser/browser_thread.h"
 #include "crypto/random.h"
 #include "google_apis/gaia/google_service_auth_error.h"
 
@@ -348,9 +347,12 @@ void SupervisedUserCreationControllerNew::RegistrationCallback(
     creation_context_->token = token;
 
     PostTaskAndReplyWithResult(
-        content::BrowserThread::GetBlockingPool()
-            ->GetTaskRunnerWithShutdownBehavior(
-                  base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN)
+        base::CreateTaskRunnerWithTraits(
+            base::TaskTraits()
+                .MayBlock()
+                .WithPriority(base::TaskPriority::BACKGROUND)
+                .WithShutdownBehavior(
+                    base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN))
             .get(),
         FROM_HERE,
         base::Bind(&StoreSupervisedUserFiles, creation_context_->token,