[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/single_thread_task_runner.h"
+#include "base/task_scheduler/lazy_task_runner.h"
+#include "base/task_scheduler/single_thread_task_runner_thread_mode.h"
+
+namespace extensions {
+
+namespace {
+
+base::SingleThreadTaskRunner* g_task_runner_for_testing = nullptr;
+
+base::LazySingleThreadTaskRunner g_task_runner =
+    LAZY_SINGLE_THREAD_TASK_RUNNER_INITIALIZER(
+        base::TaskTraits({base::MayBlock(), base::TaskPriority::BACKGROUND}),
+        base::SingleThreadTaskRunnerThreadMode::SHARED);
+
+}  // namespace
+
+const scoped_refptr<base::SingleThreadTaskRunner> GetActivityLogTaskRunner() {
+  if (g_task_runner_for_testing)
+    return g_task_runner_for_testing;
+
+  return g_task_runner.Get();
+}
+
+void SetActivityLogTaskRunnerForTesting(
+    base::SingleThreadTaskRunner* task_runner) {
+  g_task_runner_for_testing = task_runner;
+}
+
+}  // namespace extensions