[Extensions][TaskScheduler] Update ActivityLog for scheduling migration

chrome/browser/extensions/activity_log/activity_log_task_runner.h

+// 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.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_LOG_TASK_RUNNER_H_
+#define CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_LOG_TASK_RUNNER_H_
+
+#include "base/memory/ref_counted.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace extensions {
+
+// TODO(devlin): Similar to below, it's possible that SQL doesn't like running
+// on multiple threads. We *might* be able to change this to a
+// SequencedTaskRunner, but more investigation is needed.
+const scoped_refptr<base::SingleThreadTaskRunner> GetActivityLogTaskRunner();
+
+// TODO(devlin): It would be great to remove this, but we can't create a valid
+// SQL database in unittests using the normal ActivityLogTaskRunner. Might be
+// related to https://crbug.com/739945.
+void SetActivityLogTaskRunnerForTesting(
+    base::SingleThreadTaskRunner* task_runner);
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_LOG_TASK_RUNNER_H_