Migrate Extensions code to Task Scheduler API

chrome/browser/extensions/api/storage/backend_task_runner.cc

Index: chrome/browser/extensions/api/storage/backend_task_runner.cc
diff --git a/chrome/browser/extensions/api/storage/backend_task_runner.cc b/chrome/browser/extensions/api/storage/backend_task_runner.cc
deleted file mode 100644
index f565f777dd03353c3e1b45d39a4bd7ee9aa5c737..0000000000000000000000000000000000000000
--- a/chrome/browser/extensions/api/storage/backend_task_runner.cc
+++ /dev/null
@@ -1,18 +0,0 @@
-// 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/api/storage/backend_task_runner.h"
-
-#include "content/public/browser/browser_thread.h"
-
-namespace extensions {
-
-// TODO(stanisc): crbug.com/731903: change to LazySequencedTaskRunner once
-// migration from BrowserThread::FILE to GetBackendTaskRunner() is complete.
-scoped_refptr<base::SequencedTaskRunner> GetBackendTaskRunner() {
-  return content::BrowserThread::GetTaskRunnerForThread(
-      content::BrowserThread::FILE);
-}
-
-}  // namespace extensions