Implement PostDelayedTaskAt for guaranteed timer ordering

components/scheduler/child/null_worker_scheduler.cc

 // Copyright 2014 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 "components/scheduler/child/null_worker_scheduler.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/thread_task_runner_handle.h"
 #include "components/scheduler/child/null_idle_task_runner.h"
+#include "components/scheduler/child/null_task_queue.h"
 
 namespace scheduler {
 
 NullWorkerScheduler::NullWorkerScheduler()
-    : task_runner_(base::ThreadTaskRunnerHandle::Get()),
+    : task_runner_(new NullTaskQueue(base::ThreadTaskRunnerHandle::Get())),
       idle_task_runner_(new NullIdleTaskRunner()) {
 }
 
 NullWorkerScheduler::~NullWorkerScheduler() {
 }
 
-scoped_refptr<base::SingleThreadTaskRunner>
-NullWorkerScheduler::DefaultTaskRunner() {
+scoped_refptr<TaskQueue> NullWorkerScheduler::DefaultTaskRunner() {
   return task_runner_;
 }
 
 scoped_refptr<SingleThreadIdleTaskRunner>
 NullWorkerScheduler::IdleTaskRunner() {
   return idle_task_runner_;
 }
 
 void NullWorkerScheduler::AddTaskObserver(
     base::MessageLoop::TaskObserver* task_observer) {
@@ skipping 13 matching lines @@
   return false;
 }
 
 void NullWorkerScheduler::Init() {
 }
 
 void NullWorkerScheduler::Shutdown() {
 }
 
 }  // namespace scheduler