[Extensions][TaskScheduler] Update ActivityLog for scheduling migration

chrome/browser/extensions/activity_log/activity_log_task_runner.cc

+// Copyright 2017 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/activity_log/activity_log_task_runner.h"
+
+#include "base/sequenced_task_runner.h"
+#include "base/task_scheduler/lazy_task_runner.h"
+
+namespace extensions {
+
+const scoped_refptr<base::TaskRunner> GetActivityLogTaskRunner() {
+  static base::LazySequencedTaskRunner task_runner =
+      LAZY_SEQUENCED_TASK_RUNNER_INITIALIZER(
+          base::TaskTraits({base::MayBlock(), base::WithBaseSyncPrimitives(),
+                            base::TaskPriority::BACKGROUND}));
+  return task_runner.Get();
+}
+
+}  // namespace extensions