Introduce a SchedulerHelper in content/child/scheduler

content/renderer/scheduler/task_queue_manager.cc

Index: content/renderer/scheduler/task_queue_manager.cc
diff --git a/content/renderer/scheduler/task_queue_manager.cc b/content/renderer/scheduler/task_queue_manager.cc
deleted file mode 100644
index 60ae5656c1faf16e8baad3fe1e86b5145783fc07..0000000000000000000000000000000000000000
--- a/content/renderer/scheduler/task_queue_manager.cc
+++ /dev/null
@@ -1,707 +0,0 @@
-// 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 "content/renderer/scheduler/task_queue_manager.h"
-
-#include <queue>
-#include <set>
-
-#include "base/bind.h"
-#include "base/trace_event/trace_event.h"
-#include "base/trace_event/trace_event_argument.h"
-#include "cc/test/test_now_source.h"
-#include "content/renderer/scheduler/nestable_single_thread_task_runner.h"
-#include "content/renderer/scheduler/task_queue_selector.h"
-
-namespace {
-const int64_t kMaxTimeTicks = std::numeric_limits<int64>::max();
-}
-
-namespace content {
-namespace internal {
-
-// Now() is somewhat expensive so it makes sense not to call Now() unless we
-// really need to.
-class LazyNow {
- public:
-  explicit LazyNow(base::TimeTicks now)
-      : task_queue_manager_(nullptr), now_(now) {
-    DCHECK(!now.is_null());
-  }
-
-  explicit LazyNow(TaskQueueManager* task_queue_manager)
-      : task_queue_manager_(task_queue_manager) {}
-
-  base::TimeTicks Now() {
-    if (now_.is_null())
-      now_ = task_queue_manager_->Now();
-    return now_;
-  }
-
- private:
-  TaskQueueManager* task_queue_manager_;  // NOT OWNED
-  base::TimeTicks now_;
-};
-
-class TaskQueue : public base::SingleThreadTaskRunner {
- public:
-  TaskQueue(TaskQueueManager* task_queue_manager);
-
-  // base::SingleThreadTaskRunner implementation.
-  bool RunsTasksOnCurrentThread() const override;
-  bool PostDelayedTask(const tracked_objects::Location& from_here,
-                       const base::Closure& task,
-                       base::TimeDelta delay) override {
-    return PostDelayedTaskImpl(from_here, task, delay, TaskType::NORMAL);
-  }
-
-  bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
-                                  const base::Closure& task,
-                                  base::TimeDelta delay) override {
-    return PostDelayedTaskImpl(from_here, task, delay, TaskType::NON_NESTABLE);
-  }
-
-  bool IsQueueEmpty() const;
-
-  void SetPumpPolicy(TaskQueueManager::PumpPolicy pump_policy);
-  void PumpQueue();
-
-  bool NextPendingDelayedTaskRunTime(
-      base::TimeTicks* next_pending_delayed_task);
-
-  bool UpdateWorkQueue(LazyNow* lazy_now,
-                       const base::PendingTask* previous_task);
-  base::PendingTask TakeTaskFromWorkQueue();
-
-  void WillDeleteTaskQueueManager();
-
-  base::TaskQueue& work_queue() { return work_queue_; }
-
-  void set_name(const char* name) { name_ = name; }
-
-  void AsValueInto(base::trace_event::TracedValue* state) const;
-
- private:
-  enum class TaskType {
-    NORMAL,
-    NON_NESTABLE,
-  };
-
-  ~TaskQueue() override;
-
-  bool PostDelayedTaskImpl(const tracked_objects::Location& from_here,
-                           const base::Closure& task,
-                           base::TimeDelta delay,
-                           TaskType task_type);
-
-  // Delayed task posted to the underlying run loop, which locks |lock_| and
-  // calls MoveReadyDelayedTasksToIncomingQueueLocked to process dealyed tasks
-  // that need to be run now.
-  void MoveReadyDelayedTasksToIncomingQueue();
-
-  // Enqueues any delayed tasks which should be run now on the incoming_queue_
-  // and calls ScheduleDelayedWorkLocked to ensure future tasks are scheduled.
-  // Must be called with |lock_| locked.
-  void MoveReadyDelayedTasksToIncomingQueueLocked(LazyNow* lazy_now);
-
-  // Posts MoveReadyDelayedTasksToIncomingQueue if there isn't already a task
-  // posted on the underlying runloop for the next task's scheduled run time.
-  void ScheduleDelayedWorkLocked(LazyNow* lazy_now);
-
-  void PumpQueueLocked();
-  bool TaskIsOlderThanQueuedTasks(const base::PendingTask* task);
-  bool ShouldAutoPumpQueueLocked(const base::PendingTask* previous_task);
-  void EnqueueTaskLocked(const base::PendingTask& pending_task);
-
-  void TraceQueueSize(bool is_locked) const;
-  static const char* PumpPolicyToString(
-      TaskQueueManager::PumpPolicy pump_policy);
-  static void QueueAsValueInto(const base::TaskQueue& queue,
-                               base::trace_event::TracedValue* state);
-  static void QueueAsValueInto(const base::DelayedTaskQueue& queue,
-                               base::trace_event::TracedValue* state);
-  static void TaskAsValueInto(const base::PendingTask& task,
-                              base::trace_event::TracedValue* state);
-
-  // This lock protects all members except the work queue and the
-  // main_thread_checker_.
-  mutable base::Lock lock_;
-  base::PlatformThreadId thread_id_;
-  TaskQueueManager* task_queue_manager_;
-  base::TaskQueue incoming_queue_;
-  TaskQueueManager::PumpPolicy pump_policy_;
-  const char* name_;
-  base::DelayedTaskQueue delayed_task_queue_;
-  std::set<base::TimeTicks> in_flight_kick_delayed_tasks_;
-
-  base::ThreadChecker main_thread_checker_;
-  base::TaskQueue work_queue_;
-
-  DISALLOW_COPY_AND_ASSIGN(TaskQueue);
-};
-
-TaskQueue::TaskQueue(TaskQueueManager* task_queue_manager)
-    : thread_id_(base::PlatformThread::CurrentId()),
-      task_queue_manager_(task_queue_manager),
-      pump_policy_(TaskQueueManager::PumpPolicy::AUTO),
-      name_(nullptr) {
-}
-
-TaskQueue::~TaskQueue() {
-}
-
-void TaskQueue::WillDeleteTaskQueueManager() {
-  base::AutoLock lock(lock_);
-  task_queue_manager_ = nullptr;
-  // TODO(scheduler-dev): Should we also clear the other queues here too?
-  delayed_task_queue_ = base::DelayedTaskQueue();
-}
-
-bool TaskQueue::RunsTasksOnCurrentThread() const {
-  base::AutoLock lock(lock_);
-  return base::PlatformThread::CurrentId() == thread_id_;
-}
-
-bool TaskQueue::PostDelayedTaskImpl(const tracked_objects::Location& from_here,
-                                    const base::Closure& task,
-                                    base::TimeDelta delay,
-                                    TaskType task_type) {
-  base::AutoLock lock(lock_);
-  if (!task_queue_manager_)
-    return false;
-
-  base::PendingTask pending_task(from_here, task, base::TimeTicks(),
-                                 task_type != TaskType::NON_NESTABLE);
-  task_queue_manager_->DidQueueTask(&pending_task);
-
-  if (delay > base::TimeDelta()) {
-    base::TimeTicks now = task_queue_manager_->Now();
-    pending_task.delayed_run_time = now + delay;
-    delayed_task_queue_.push(pending_task);
-    TraceQueueSize(true);
-    // If we changed the topmost task, then it is time to reschedule.
-    if (delayed_task_queue_.top().task.Equals(pending_task.task)) {
-      LazyNow lazy_now(now);
-      ScheduleDelayedWorkLocked(&lazy_now);
-    }
-    return true;
-  }
-  EnqueueTaskLocked(pending_task);
-  return true;
-}
-
-void TaskQueue::MoveReadyDelayedTasksToIncomingQueue() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  base::AutoLock lock(lock_);
-  if (!task_queue_manager_)
-    return;
-
-  LazyNow lazy_now(task_queue_manager_);
-  MoveReadyDelayedTasksToIncomingQueueLocked(&lazy_now);
-}
-
-void TaskQueue::MoveReadyDelayedTasksToIncomingQueueLocked(LazyNow* lazy_now) {
-  lock_.AssertAcquired();
-  // Enqueue all delayed tasks that should be running now.
-  while (!delayed_task_queue_.empty() &&
-         delayed_task_queue_.top().delayed_run_time <= lazy_now->Now()) {
-    in_flight_kick_delayed_tasks_.erase(
-        delayed_task_queue_.top().delayed_run_time);
-    EnqueueTaskLocked(delayed_task_queue_.top());
-    delayed_task_queue_.pop();
-  }
-  TraceQueueSize(true);
-  ScheduleDelayedWorkLocked(lazy_now);
-}
-
-void TaskQueue::ScheduleDelayedWorkLocked(LazyNow* lazy_now) {
-  lock_.AssertAcquired();
-  // Any remaining tasks are in the future, so queue a task to kick them.
-  if (!delayed_task_queue_.empty()) {
-    base::TimeTicks next_run_time = delayed_task_queue_.top().delayed_run_time;
-    DCHECK_GT(next_run_time, lazy_now->Now());
-    // Make sure we don't have more than one
-    // MoveReadyDelayedTasksToIncomingQueue posted for a particular scheduled
-    // run time (note it's fine to have multiple ones in flight for distinct
-    // run times).
-    if (in_flight_kick_delayed_tasks_.find(next_run_time) ==
-        in_flight_kick_delayed_tasks_.end()) {
-      in_flight_kick_delayed_tasks_.insert(next_run_time);
-      base::TimeDelta delay = next_run_time - lazy_now->Now();
-      task_queue_manager_->PostDelayedTask(
-          FROM_HERE,
-          Bind(&TaskQueue::MoveReadyDelayedTasksToIncomingQueue, this), delay);
-    }
-  }
-}
-
-bool TaskQueue::IsQueueEmpty() const {
-  if (!work_queue_.empty())
-    return false;
-
-  {
-    base::AutoLock lock(lock_);
-    return incoming_queue_.empty();
-  }
-}
-
-bool TaskQueue::TaskIsOlderThanQueuedTasks(const base::PendingTask* task) {
-  lock_.AssertAcquired();
-  // A null task is passed when UpdateQueue is called before any task is run.
-  // In this case we don't want to pump an after_wakeup queue, so return true
-  // here.
-  if (!task)
-    return true;
-
-  // Return false if there are no task in the incoming queue.
-  if (incoming_queue_.empty())
-    return false;
-
-  base::PendingTask oldest_queued_task = incoming_queue_.front();
-  DCHECK(oldest_queued_task.delayed_run_time.is_null());
-  DCHECK(task->delayed_run_time.is_null());
-
-  // Note: the comparison is correct due to the fact that the PendingTask
-  // operator inverts its comparison operation in order to work well in a heap
-  // based priority queue.
-  return oldest_queued_task < *task;
-}
-
-bool TaskQueue::ShouldAutoPumpQueueLocked(
-    const base::PendingTask* previous_task) {
-  lock_.AssertAcquired();
-  if (pump_policy_ == TaskQueueManager::PumpPolicy::MANUAL)
-    return false;
-  if (pump_policy_ == TaskQueueManager::PumpPolicy::AFTER_WAKEUP &&
-      TaskIsOlderThanQueuedTasks(previous_task))
-    return false;
-  if (incoming_queue_.empty())
-    return false;
-  return true;
-}
-
-bool TaskQueue::NextPendingDelayedTaskRunTime(
-    base::TimeTicks* next_pending_delayed_task) {
-  base::AutoLock lock(lock_);
-  if (delayed_task_queue_.empty())
-    return false;
-  *next_pending_delayed_task = delayed_task_queue_.top().delayed_run_time;
-  return true;
-}
-
-bool TaskQueue::UpdateWorkQueue(LazyNow* lazy_now,
-                                const base::PendingTask* previous_task) {
-  if (!work_queue_.empty())
-    return true;
-
-  {
-    base::AutoLock lock(lock_);
-    MoveReadyDelayedTasksToIncomingQueueLocked(lazy_now);
-    if (!ShouldAutoPumpQueueLocked(previous_task))
-      return false;
-    MoveReadyDelayedTasksToIncomingQueueLocked(lazy_now);
-    work_queue_.Swap(&incoming_queue_);
-    TraceQueueSize(true);
-    return true;
-  }
-}
-
-base::PendingTask TaskQueue::TakeTaskFromWorkQueue() {
-  base::PendingTask pending_task = work_queue_.front();
-  work_queue_.pop();
-  TraceQueueSize(false);
-  return pending_task;
-}
-
-void TaskQueue::TraceQueueSize(bool is_locked) const {
-  bool is_tracing;
-  TRACE_EVENT_CATEGORY_GROUP_ENABLED(
-      TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"), &is_tracing);
-  if (!is_tracing || !name_)
-    return;
-  if (!is_locked)
-    lock_.Acquire();
-  else
-    lock_.AssertAcquired();
-  TRACE_COUNTER1(
-      TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"), name_,
-      incoming_queue_.size() + work_queue_.size() + delayed_task_queue_.size());
-  if (!is_locked)
-    lock_.Release();
-}
-
-void TaskQueue::EnqueueTaskLocked(const base::PendingTask& pending_task) {
-  lock_.AssertAcquired();
-  if (!task_queue_manager_)
-    return;
-  if (pump_policy_ == TaskQueueManager::PumpPolicy::AUTO &&
-      incoming_queue_.empty())
-    task_queue_manager_->MaybePostDoWorkOnMainRunner();
-  incoming_queue_.push(pending_task);
-
-  if (!pending_task.delayed_run_time.is_null()) {
-    // Clear the delayed run time because we've already applied the delay
-    // before getting here.
-    incoming_queue_.back().delayed_run_time = base::TimeTicks();
-  }
-  TraceQueueSize(true);
-}
-
-void TaskQueue::SetPumpPolicy(TaskQueueManager::PumpPolicy pump_policy) {
-  base::AutoLock lock(lock_);
-  if (pump_policy == TaskQueueManager::PumpPolicy::AUTO &&
-      pump_policy_ != TaskQueueManager::PumpPolicy::AUTO) {
-    PumpQueueLocked();
-  }
-  pump_policy_ = pump_policy;
-}
-
-void TaskQueue::PumpQueueLocked() {
-  lock_.AssertAcquired();
-  if (task_queue_manager_) {
-    LazyNow lazy_now(task_queue_manager_);
-    MoveReadyDelayedTasksToIncomingQueueLocked(&lazy_now);
-  }
-  while (!incoming_queue_.empty()) {
-    work_queue_.push(incoming_queue_.front());
-    incoming_queue_.pop();
-  }
-  if (!work_queue_.empty())
-    task_queue_manager_->MaybePostDoWorkOnMainRunner();
-}
-
-void TaskQueue::PumpQueue() {
-  base::AutoLock lock(lock_);
-  PumpQueueLocked();
-}
-
-void TaskQueue::AsValueInto(base::trace_event::TracedValue* state) const {
-  base::AutoLock lock(lock_);
-  state->BeginDictionary();
-  if (name_)
-    state->SetString("name", name_);
-  state->SetString("pump_policy", PumpPolicyToString(pump_policy_));
-  state->BeginArray("incoming_queue");
-  QueueAsValueInto(incoming_queue_, state);
-  state->EndArray();
-  state->BeginArray("work_queue");
-  QueueAsValueInto(work_queue_, state);
-  state->EndArray();
-  state->BeginArray("delayed_task_queue");
-  QueueAsValueInto(delayed_task_queue_, state);
-  state->EndArray();
-  state->EndDictionary();
-}
-
-// static
-const char* TaskQueue::PumpPolicyToString(
-    TaskQueueManager::PumpPolicy pump_policy) {
-  switch (pump_policy) {
-    case TaskQueueManager::PumpPolicy::AUTO:
-      return "auto";
-    case TaskQueueManager::PumpPolicy::AFTER_WAKEUP:
-      return "after_wakeup";
-    case TaskQueueManager::PumpPolicy::MANUAL:
-      return "manual";
-    default:
-      NOTREACHED();
-      return nullptr;
-  }
-}
-
-// static
-void TaskQueue::QueueAsValueInto(const base::TaskQueue& queue,
-                                 base::trace_event::TracedValue* state) {
-  base::TaskQueue queue_copy(queue);
-  while (!queue_copy.empty()) {
-    TaskAsValueInto(queue_copy.front(), state);
-    queue_copy.pop();
-  }
-}
-
-// static
-void TaskQueue::QueueAsValueInto(const base::DelayedTaskQueue& queue,
-                                 base::trace_event::TracedValue* state) {
-  base::DelayedTaskQueue queue_copy(queue);
-  while (!queue_copy.empty()) {
-    TaskAsValueInto(queue_copy.top(), state);
-    queue_copy.pop();
-  }
-}
-
-// static
-void TaskQueue::TaskAsValueInto(const base::PendingTask& task,
-                                base::trace_event::TracedValue* state) {
-  state->BeginDictionary();
-  state->SetString("posted_from", task.posted_from.ToString());
-  state->SetInteger("sequence_num", task.sequence_num);
-  state->SetBoolean("nestable", task.nestable);
-  state->SetBoolean("is_high_res", task.is_high_res);
-  state->SetDouble(
-      "delayed_run_time",
-      (task.delayed_run_time - base::TimeTicks()).InMicroseconds() / 1000.0L);
-  state->EndDictionary();
-}
-
-}  // namespace internal
-
-TaskQueueManager::TaskQueueManager(
-    size_t task_queue_count,
-    scoped_refptr<NestableSingleThreadTaskRunner> main_task_runner,
-    TaskQueueSelector* selector)
-    : main_task_runner_(main_task_runner),
-      selector_(selector),
-      pending_dowork_count_(0),
-      work_batch_size_(1),
-      time_source_(nullptr),
-      weak_factory_(this) {
-  DCHECK(main_task_runner->RunsTasksOnCurrentThread());
-  TRACE_EVENT_OBJECT_CREATED_WITH_ID(
-      TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"), "TaskQueueManager",
-      this);
-
-  task_queue_manager_weak_ptr_ = weak_factory_.GetWeakPtr();
-  for (size_t i = 0; i < task_queue_count; i++) {
-    scoped_refptr<internal::TaskQueue> queue(
-        make_scoped_refptr(new internal::TaskQueue(this)));
-    queues_.push_back(queue);
-  }
-
-  std::vector<const base::TaskQueue*> work_queues;
-  for (const auto& queue: queues_)
-    work_queues.push_back(&queue->work_queue());
-  selector_->RegisterWorkQueues(work_queues);
-}
-
-TaskQueueManager::~TaskQueueManager() {
-  TRACE_EVENT_OBJECT_DELETED_WITH_ID(
-      TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"), "TaskQueueManager",
-      this);
-  for (auto& queue : queues_)
-    queue->WillDeleteTaskQueueManager();
-}
-
-internal::TaskQueue* TaskQueueManager::Queue(size_t queue_index) const {
-  DCHECK_LT(queue_index, queues_.size());
-  return queues_[queue_index].get();
-}
-
-scoped_refptr<base::SingleThreadTaskRunner>
-TaskQueueManager::TaskRunnerForQueue(size_t queue_index) const {
-  return Queue(queue_index);
-}
-
-bool TaskQueueManager::IsQueueEmpty(size_t queue_index) const {
-  internal::TaskQueue* queue = Queue(queue_index);
-  return queue->IsQueueEmpty();
-}
-
-base::TimeTicks TaskQueueManager::NextPendingDelayedTaskRunTime() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  bool found_pending_task = false;
-  base::TimeTicks next_pending_delayed_task(
-      base::TimeTicks::FromInternalValue(kMaxTimeTicks));
-  for (auto& queue : queues_) {
-    base::TimeTicks queues_next_pending_delayed_task;
-    if (queue->NextPendingDelayedTaskRunTime(
-            &queues_next_pending_delayed_task)) {
-      found_pending_task = true;
-      next_pending_delayed_task =
-          std::min(next_pending_delayed_task, queues_next_pending_delayed_task);
-    }
-  }
-
-  if (!found_pending_task)
-    return base::TimeTicks();
-
-  DCHECK_NE(next_pending_delayed_task,
-            base::TimeTicks::FromInternalValue(kMaxTimeTicks));
-  return next_pending_delayed_task;
-}
-
-void TaskQueueManager::SetPumpPolicy(size_t queue_index,
-                                     PumpPolicy pump_policy) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  internal::TaskQueue* queue = Queue(queue_index);
-  queue->SetPumpPolicy(pump_policy);
-}
-
-void TaskQueueManager::PumpQueue(size_t queue_index) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  internal::TaskQueue* queue = Queue(queue_index);
-  queue->PumpQueue();
-}
-
-bool TaskQueueManager::UpdateWorkQueues(
-    const base::PendingTask* previous_task) {
-  // TODO(skyostil): This is not efficient when the number of queues grows very
-  // large due to the number of locks taken. Consider optimizing when we get
-  // there.
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  internal::LazyNow lazy_now(this);
-  bool has_work = false;
-  for (auto& queue : queues_) {
-    has_work |= queue->UpdateWorkQueue(&lazy_now, previous_task);
-    if (!queue->work_queue().empty()) {
-      // Currently we should not be getting tasks with delayed run times in any
-      // of the work queues.
-      DCHECK(queue->work_queue().front().delayed_run_time.is_null());
-    }
-  }
-  return has_work;
-}
-
-void TaskQueueManager::MaybePostDoWorkOnMainRunner() {
-  bool on_main_thread = main_task_runner_->BelongsToCurrentThread();
-  if (on_main_thread) {
-    // We only want one pending DoWork posted from the main thread, or we risk
-    // an explosion of pending DoWorks which could starve out everything else.
-    if (pending_dowork_count_ > 0) {
-      return;
-    }
-    pending_dowork_count_++;
-  }
-
-  main_task_runner_->PostTask(
-      FROM_HERE, Bind(&TaskQueueManager::DoWork, task_queue_manager_weak_ptr_,
-                      on_main_thread));
-}
-
-void TaskQueueManager::DoWork(bool posted_from_main_thread) {
-  if (posted_from_main_thread) {
-    pending_dowork_count_--;
-    DCHECK_GE(pending_dowork_count_, 0);
-  }
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-
-  // Pass nullptr to UpdateWorkQueues here to prevent waking up a
-  // pump-after-wakeup queue.
-  if (!UpdateWorkQueues(nullptr))
-    return;
-
-  base::PendingTask previous_task((tracked_objects::Location()),
-                                  (base::Closure()));
-  for (int i = 0; i < work_batch_size_; i++) {
-    size_t queue_index;
-    if (!SelectWorkQueueToService(&queue_index))
-      return;
-    // Note that this function won't post another call to DoWork if one is
-    // already pending, so it is safe to call it in a loop.
-    MaybePostDoWorkOnMainRunner();
-    ProcessTaskFromWorkQueue(queue_index, i > 0, &previous_task);
-
-    if (!UpdateWorkQueues(&previous_task))
-      return;
-  }
-}
-
-bool TaskQueueManager::SelectWorkQueueToService(size_t* out_queue_index) {
-  bool should_run = selector_->SelectWorkQueueToService(out_queue_index);
-  TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(
-      TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"), "TaskQueueManager", this,
-      AsValueWithSelectorResult(should_run, *out_queue_index));
-  return should_run;
-}
-
-void TaskQueueManager::DidQueueTask(base::PendingTask* pending_task) {
-  pending_task->sequence_num = task_sequence_num_.GetNext();
-  task_annotator_.DidQueueTask("TaskQueueManager::PostTask", *pending_task);
-}
-
-void TaskQueueManager::ProcessTaskFromWorkQueue(
-    size_t queue_index,
-    bool has_previous_task,
-    base::PendingTask* previous_task) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  internal::TaskQueue* queue = Queue(queue_index);
-  base::PendingTask pending_task = queue->TakeTaskFromWorkQueue();
-  if (!pending_task.nestable && main_task_runner_->IsNested()) {
-    // Defer non-nestable work to the main task runner.  NOTE these tasks can be
-    // arbitrarily delayed so the additional delay should not be a problem.
-    main_task_runner_->PostNonNestableTask(pending_task.posted_from,
-                                           pending_task.task);
-  } else {
-    // Suppress "will" task observer notifications for the first and "did"
-    // notifications for the last task in the batch to avoid duplicate
-    // notifications.
-    if (has_previous_task) {
-      FOR_EACH_OBSERVER(base::MessageLoop::TaskObserver, task_observers_,
-                        DidProcessTask(*previous_task));
-      FOR_EACH_OBSERVER(base::MessageLoop::TaskObserver, task_observers_,
-                        WillProcessTask(pending_task));
-    }
-    task_annotator_.RunTask("TaskQueueManager::PostTask",
-                            "TaskQueueManager::RunTask", pending_task);
-    pending_task.task.Reset();
-    *previous_task = pending_task;
-  }
-}
-
-bool TaskQueueManager::RunsTasksOnCurrentThread() const {
-  return main_task_runner_->RunsTasksOnCurrentThread();
-}
-
-bool TaskQueueManager::PostDelayedTask(
-    const tracked_objects::Location& from_here,
-    const base::Closure& task,
-    base::TimeDelta delay) {
-  DCHECK(delay > base::TimeDelta());
-  return main_task_runner_->PostDelayedTask(from_here, task, delay);
-}
-
-void TaskQueueManager::SetQueueName(size_t queue_index, const char* name) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  internal::TaskQueue* queue = Queue(queue_index);
-  queue->set_name(name);
-}
-
-void TaskQueueManager::SetWorkBatchSize(int work_batch_size) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  DCHECK_GE(work_batch_size, 1);
-  work_batch_size_ = work_batch_size;
-}
-
-void TaskQueueManager::AddTaskObserver(
-    base::MessageLoop::TaskObserver* task_observer) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  base::MessageLoop::current()->AddTaskObserver(task_observer);
-  task_observers_.AddObserver(task_observer);
-}
-
-void TaskQueueManager::RemoveTaskObserver(
-    base::MessageLoop::TaskObserver* task_observer) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  base::MessageLoop::current()->RemoveTaskObserver(task_observer);
-  task_observers_.RemoveObserver(task_observer);
-}
-
-void TaskQueueManager::SetTimeSourceForTesting(
-    scoped_refptr<cc::TestNowSource> time_source) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  time_source_ = time_source;
-}
-
-base::TimeTicks TaskQueueManager::Now() const {
-  return UNLIKELY(time_source_) ? time_source_->Now() : base::TimeTicks::Now();
-}
-
-scoped_refptr<base::trace_event::ConvertableToTraceFormat>
-TaskQueueManager::AsValueWithSelectorResult(bool should_run,
-                                            size_t selected_queue) const {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  scoped_refptr<base::trace_event::TracedValue> state =
-      new base::trace_event::TracedValue();
-  state->BeginArray("queues");
-  for (auto& queue : queues_)
-    queue->AsValueInto(state.get());
-  state->EndArray();
-  state->BeginDictionary("selector");
-  selector_->AsValueInto(state.get());
-  state->EndDictionary();
-  if (should_run)
-    state->SetInteger("selected_queue", selected_queue);
-  return state;
-}
-
-}  // namespace content