Revert of Make canceling Timers fast.

third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.cc

 // Copyright 2015 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 "platform/scheduler/base/task_queue_impl.h"
 
 #include "base/trace_event/blame_context.h"
 #include "platform/scheduler/base/task_queue_manager.h"
 #include "platform/scheduler/base/task_queue_manager_delegate.h"
 #include "platform/scheduler/base/time_domain.h"
 #include "platform/scheduler/base/work_queue.h"
 
 namespace blink {
 namespace scheduler {
 
+TaskQueue::TaskHandle::TaskHandle() : enqueue_order_(0), sequence_number_(0) {}
+
+TaskQueue::TaskHandle::TaskHandle(TaskQueue* task_queue, uint64_t enqueue_order)
+    : enqueue_order_(enqueue_order),
+#if DCHECK_IS_ON()
+      task_queue_(task_queue),
+#endif
+      sequence_number_(0) {
+  DCHECK_GT(enqueue_order, 0ull);
+}
+
+TaskQueue::TaskHandle::TaskHandle(TaskQueue* task_queue,
+                                  base::TimeTicks scheduled_run_time,
+                                  int sequence_number)
+    : enqueue_order_(0),
+      scheduled_run_time_(scheduled_run_time),
+#if DCHECK_IS_ON()
+      task_queue_(task_queue),
+#endif
+      sequence_number_(sequence_number) {
+  DCHECK(!scheduled_run_time.is_null());
+}
+
+TaskQueue::TaskHandle::operator bool() const {
+  return !scheduled_run_time_.is_null() ||
+         internal::EnqueueOrderGenerator::IsValidEnqueueOrder(enqueue_order_);
+}
+
 namespace internal {
 
 TaskQueueImpl::TaskQueueImpl(
     TaskQueueManager* task_queue_manager,
     TimeDomain* time_domain,
     const Spec& spec,
     const char* disabled_by_default_tracing_category,
     const char* disabled_by_default_verbose_tracing_category)
     : thread_id_(base::PlatformThread::CurrentId()),
       any_thread_(task_queue_manager, time_domain),
@@ skipping 55 matching lines @@
                           bool nestable,
                           EnqueueOrder enqueue_order)
     : PendingTask(posted_from, task, desired_run_time, nestable),
 #ifndef NDEBUG
       enqueue_order_set_(true),
 #endif
       enqueue_order_(enqueue_order) {
   sequence_num = sequence_number;
 }
 
+// static
+TaskQueueImpl::Task TaskQueueImpl::Task::CreateFakeTaskFromHandle(
+    const TaskHandle& handle) {
+  if (handle.scheduled_run_time_.is_null()) {
+    // It's an immediate task.
+    return Task(tracked_objects::Location(), base::Closure(),
+                handle.scheduled_run_time_, handle.sequence_number_, false,
+                handle.enqueue_order_);
+  } else {
+    // It's a delayed task.
+    DCHECK_EQ(0ull, handle.enqueue_order_);
+    return Task(tracked_objects::Location(), base::Closure(),
+                handle.scheduled_run_time_, handle.sequence_number_, false);
+  }
+}
+
+bool TaskQueueImpl::Task::DelayedRunTimeComparator::operator()(
+    const Task& a,
+    const Task& b) const {
+  if (a.delayed_run_time < b.delayed_run_time)
+    return true;
+
+  if (a.delayed_run_time > b.delayed_run_time)
+    return false;
+
+  // If the times happen to match, then we use the sequence number to decide.
+  // Compare the difference to support integer roll-over.
+  return (a.sequence_num - b.sequence_num) < 0;
+}
+
+// static
+bool TaskQueueImpl::Task::EnqueueOrderComparatorFn(const Task& a,
+                                                   const Task& b) {
+  return a.enqueue_order() < b.enqueue_order();
+}
+
+// static
+bool TaskQueueImpl::Task::DelayedRunTimeComparatorFn(const Task& a,
+                                                     const Task& b) {
+  if (a.delayed_run_time < b.delayed_run_time)
+    return true;
+
+  if (a.delayed_run_time > b.delayed_run_time)
+    return false;
+
+  // If the times happen to match, then we use the sequence number to decide.
+  // Compare the difference to support integer roll-over.
+  return (a.sequence_num - b.sequence_num) < 0;
+}
+
 TaskQueueImpl::AnyThread::AnyThread(TaskQueueManager* task_queue_manager,
                                     TimeDomain* time_domain)
-    : task_queue_manager(task_queue_manager), time_domain(time_domain) {}
+    : task_queue_manager(task_queue_manager),
+      time_domain(time_domain),
+      immediate_incoming_queue(&TaskQueueImpl::Task::EnqueueOrderComparatorFn) {
+}
 
 TaskQueueImpl::AnyThread::~AnyThread() {}
 
 TaskQueueImpl::MainThreadOnly::MainThreadOnly(
     TaskQueueManager* task_queue_manager,
     TaskQueueImpl* task_queue,
     TimeDomain* time_domain)
     : task_queue_manager(task_queue_manager),
       time_domain(time_domain),
-      delayed_work_queue(new WorkQueue(task_queue, "delayed")),
-      immediate_work_queue(new WorkQueue(task_queue, "immediate")),
+      delayed_work_queue(
+          new WorkQueue(task_queue,
+                        "delayed",
+                        &TaskQueueImpl::Task::DelayedRunTimeComparatorFn)),
+      immediate_work_queue(
+          new WorkQueue(task_queue,
+                        "immediate",
+                        &TaskQueueImpl::Task::EnqueueOrderComparatorFn)),
       set_index(0),
       is_enabled(true),
       blame_context(nullptr),
       current_fence(0) {}
 
 TaskQueueImpl::MainThreadOnly::~MainThreadOnly() {}
 
 void TaskQueueImpl::UnregisterTaskQueue() {
   base::AutoLock lock(any_thread_lock_);
   if (main_thread_only().time_domain)
     main_thread_only().time_domain->UnregisterQueue(this);
   if (!any_thread().task_queue_manager)
     return;
   any_thread().time_domain = nullptr;
   main_thread_only().time_domain = nullptr;
   any_thread().task_queue_manager->UnregisterTaskQueue(this);
 
   any_thread().task_queue_manager = nullptr;
   main_thread_only().task_queue_manager = nullptr;
-  main_thread_only().delayed_incoming_queue = std::priority_queue<Task>();
-  any_thread().immediate_incoming_queue = std::queue<Task>();
+  main_thread_only().delayed_incoming_queue.clear();
+  any_thread().immediate_incoming_queue.clear();
   main_thread_only().immediate_work_queue.reset();
   main_thread_only().delayed_work_queue.reset();
 }
 
 bool TaskQueueImpl::RunsTasksOnCurrentThread() const {
   base::AutoLock lock(any_thread_lock_);
   return base::PlatformThread::CurrentId() == thread_id_;
 }
 
+TaskQueue::TaskHandle TaskQueueImpl::PostCancellableDelayedTask(
+    const tracked_objects::Location& from_here,
+    const base::Closure& task,
+    base::TimeDelta delay) {
+  if (!main_thread_only().task_queue_manager)
+    return TaskHandle();
+
+  EnqueueOrder sequence_number =
+      main_thread_only().task_queue_manager->GetNextSequenceNumber();
+
+  if (delay.is_zero()) {
+    base::AutoLock lock(any_thread_lock_);
+    PushOntoImmediateIncomingQueueLocked(
+        Task(from_here, task, base::TimeTicks(), sequence_number, true,
+             sequence_number));
+
+    return TaskHandle(this, sequence_number);
+  } else {
+    DCHECK_GT(delay, base::TimeDelta());
+    base::TimeTicks time_domain_now = main_thread_only().time_domain->Now();
+    base::TimeTicks time_domain_delayed_run_time = time_domain_now + delay;
+    PushOntoDelayedIncomingQueueFromMainThread(
+        Task(from_here, task, time_domain_delayed_run_time, sequence_number,
+             true),
+        time_domain_now);
+
+    return TaskHandle(this, time_domain_delayed_run_time, sequence_number);
+  }
+}
+
+bool TaskQueueImpl::CancelTask(const TaskQueue::TaskHandle& handle) {
+  if (!handle)
+    return false;
+
+  // If the TaskQueueManager has gone away, pretend we have canceled the task
+  // because this simplifies logic in TimerBase::stop.
+  if (!main_thread_only().task_queue_manager)
+    return true;
+
+#if DCHECK_IS_ON()
+  DCHECK_EQ(handle.task_queue_, this);
+#endif
+
+  Task fake_task = Task::CreateFakeTaskFromHandle(handle);
+  if (handle.scheduled_run_time_.is_null()) {
+    // It's an immediate task.
+    if (main_thread_only().immediate_work_queue->CancelTask(fake_task))
+      return true;
+
+    base::AutoLock lock(any_thread_lock_);
+    return any_thread().immediate_incoming_queue.erase(fake_task) > 0;
+  } else {
+    // It's a delayed task.
+    DelayedRunTimeQueue::iterator it =
+        main_thread_only().delayed_incoming_queue.find(fake_task);
+    if (it != main_thread_only().delayed_incoming_queue.end()) {
+      // It's safe to remove the wakeup from the TimeDomain only if this task's
+      // scheduled run time was unique within the queue.
+      bool can_cancel_timedomain_wakeup = true;
+      if (it != main_thread_only().delayed_incoming_queue.begin()) {
+        DelayedRunTimeQueue::iterator before = it;
+        before--;
+        if (before->delayed_run_time == handle.scheduled_run_time_)
+          can_cancel_timedomain_wakeup = false;
+      }
+      if (can_cancel_timedomain_wakeup) {
+        DelayedRunTimeQueue::iterator after = it;
+        after++;
+        if (after != main_thread_only().delayed_incoming_queue.end() &&
+            after->delayed_run_time == handle.scheduled_run_time_) {
+          can_cancel_timedomain_wakeup = false;
+        }
+      }
+      if (can_cancel_timedomain_wakeup) {
+        main_thread_only().time_domain->CancelDelayedWork(
+            this, handle.scheduled_run_time_);
+      }
+
+      main_thread_only().delayed_incoming_queue.erase(it);
+      return true;
+    }
+
+    return main_thread_only().delayed_work_queue->CancelTask(fake_task);
+  }
+}
+
+bool TaskQueueImpl::IsTaskPending(const TaskQueue::TaskHandle& handle) const {
+  if (!handle)
+    return false;
+
+  // If the TaskQueueManager has gone away the task got cancelled.
+  if (!main_thread_only().task_queue_manager)
+    return false;
+
+#if DCHECK_IS_ON()
+  DCHECK_EQ(handle.task_queue_, this);
+#endif
+
+  Task fake_task = Task::CreateFakeTaskFromHandle(handle);
+  if (handle.scheduled_run_time_.is_null()) {
+    // It's an immediate task.
+    if (main_thread_only().immediate_work_queue->IsTaskPending(fake_task))
+      return true;
+
+    base::AutoLock lock(any_thread_lock_);
+    return any_thread().immediate_incoming_queue.find(fake_task) !=
+           any_thread().immediate_incoming_queue.end();
+  } else {
+    // It's a delayed task.
+    DelayedRunTimeQueue::iterator it =
+        main_thread_only().delayed_incoming_queue.find(fake_task);
+    if (it != main_thread_only().delayed_incoming_queue.end())
+      return true;
+
+    return main_thread_only().delayed_work_queue->IsTaskPending(fake_task);
+  }
+}
 
 bool TaskQueueImpl::PostDelayedTask(const tracked_objects::Location& from_here,
                                     const base::Closure& task,
                                     base::TimeDelta delay) {
   if (delay.is_zero())
     return PostImmediateTaskImpl(from_here, task, TaskType::NORMAL);
 
   return PostDelayedTaskImpl(from_here, task, delay, TaskType::NORMAL);
 }
 
@@ skipping 12 matching lines @@
     const base::Closure& task,
     TaskType task_type) {
   base::AutoLock lock(any_thread_lock_);
   if (!any_thread().task_queue_manager)
     return false;
 
   EnqueueOrder sequence_number =
       any_thread().task_queue_manager->GetNextSequenceNumber();
 
   PushOntoImmediateIncomingQueueLocked(
-      from_here,
-      task,
-      base::TimeTicks(),
-      sequence_number,
-      task_type != TaskType::NON_NESTABLE);
+      Task(from_here, task, base::TimeTicks(), sequence_number,
+           task_type != TaskType::NON_NESTABLE, sequence_number));
   return true;
 }
 
 bool TaskQueueImpl::PostDelayedTaskImpl(
     const tracked_objects::Location& from_here,
     const base::Closure& task,
     base::TimeDelta delay,
     TaskType task_type) {
   DCHECK_GT(delay, base::TimeDelta());
   if (base::PlatformThread::CurrentId() == thread_id_) {
@@ skipping 25 matching lines @@
     base::TimeTicks time_domain_now = any_thread().time_domain->Now();
     base::TimeTicks time_domain_delayed_run_time = time_domain_now + delay;
     PushOntoDelayedIncomingQueueLocked(
         Task(from_here, task, time_domain_delayed_run_time, sequence_number,
              task_type != TaskType::NON_NESTABLE));
   }
   return true;
 }
 
 void TaskQueueImpl::PushOntoDelayedIncomingQueueFromMainThread(
-    Task pending_task, base::TimeTicks now) {
+    Task pending_task,
+    base::TimeTicks now) {
   main_thread_only().task_queue_manager->DidQueueTask(pending_task);
 
   // Schedule a later call to MoveReadyDelayedTasksToDelayedWorkQueue.
   base::TimeTicks delayed_run_time = pending_task.delayed_run_time;
-  main_thread_only().delayed_incoming_queue.push(std::move(pending_task));
+  main_thread_only().delayed_incoming_queue.insert(std::move(pending_task));
   main_thread_only().time_domain->ScheduleDelayedWork(this, delayed_run_time,
                                                       now);
   TraceQueueSize(false);
 }
 
 void TaskQueueImpl::PushOntoDelayedIncomingQueueLocked(Task pending_task) {
   any_thread().task_queue_manager->DidQueueTask(pending_task);
 
   int thread_hop_task_sequence_number =
       any_thread().task_queue_manager->GetNextSequenceNumber();
   PushOntoImmediateIncomingQueueLocked(
-     FROM_HERE,
-     base::Bind(&TaskQueueImpl::ScheduleDelayedWorkTask, this,
-                base::Passed(&pending_task)),
-     base::TimeTicks(),
-     thread_hop_task_sequence_number,
-     false);
+      Task(FROM_HERE, base::Bind(&TaskQueueImpl::ScheduleDelayedWorkTask, this,
+                                 base::Passed(&pending_task)),
+           base::TimeTicks(), thread_hop_task_sequence_number, false,
+           thread_hop_task_sequence_number));
 }
 
-void TaskQueueImpl::PushOntoImmediateIncomingQueueLocked(
-         const tracked_objects::Location& posted_from,
-         const base::Closure& task,
-         base::TimeTicks desired_run_time,
-         EnqueueOrder sequence_number,
-         bool nestable) {
+void TaskQueueImpl::PushOntoImmediateIncomingQueueLocked(Task pending_task) {
   if (any_thread().immediate_incoming_queue.empty())
     any_thread().time_domain->RegisterAsUpdatableTaskQueue(this);
   // If the |immediate_incoming_queue| is empty we need a DoWork posted to make
   // it run.
   if (any_thread().immediate_incoming_queue.empty()) {
     // There's no point posting a DoWork for a disabled queue, however we can
     // only tell if it's disabled from the main thread.
     if (base::PlatformThread::CurrentId() == thread_id_) {
       if (main_thread_only().is_enabled && !BlockedByFenceLocked())
         any_thread().task_queue_manager->MaybeScheduleImmediateWork(FROM_HERE);
     } else {
       any_thread().task_queue_manager->MaybeScheduleImmediateWork(FROM_HERE);
     }
   }
-  any_thread().immediate_incoming_queue.emplace(
-      posted_from, task, desired_run_time, sequence_number, nestable, sequence_number);
-  any_thread().task_queue_manager->DidQueueTask( any_thread().immediate_incoming_queue.back());
+  any_thread().task_queue_manager->DidQueueTask(pending_task);
+  // We expect |pending_task| to be inserted at the end. Amoritized O(1).
+  any_thread().immediate_incoming_queue.insert(
+      any_thread().immediate_incoming_queue.end(),
+      std::move(pending_task));
+  DCHECK_EQ(pending_task.enqueue_order(),
+            any_thread().immediate_incoming_queue.rbegin()->enqueue_order());
   TraceQueueSize(true);
 }
 
 void TaskQueueImpl::ScheduleDelayedWorkTask(Task pending_task) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
   base::TimeTicks delayed_run_time = pending_task.delayed_run_time;
   base::TimeTicks time_domain_now = main_thread_only().time_domain->Now();
   // Make sure |delayed_run_time| isn't in the past.
   if (delayed_run_time < time_domain_now) {
     delayed_run_time = time_domain_now;
     pending_task.delayed_run_time = time_domain_now;
-    main_thread_only().delayed_incoming_queue.push(std::move(pending_task));
+    main_thread_only().delayed_incoming_queue.insert(std::move(pending_task));
     LazyNow lazy_now(time_domain_now);
     MoveReadyDelayedTasksToDelayedWorkQueue(&lazy_now);
   } else {
-    main_thread_only().delayed_incoming_queue.push(std::move(pending_task));
+    main_thread_only().delayed_incoming_queue.insert(std::move(pending_task));
     main_thread_only().time_domain->ScheduleDelayedWork(
         this, delayed_run_time, main_thread_only().time_domain->Now());
   }
   TraceQueueSize(false);
 }
 
 void TaskQueueImpl::SetQueueEnabled(bool enabled) {
   if (main_thread_only().is_enabled == enabled)
     return;
   main_thread_only().is_enabled = enabled;
   if (!main_thread_only().task_queue_manager)
     return;
   if (enabled) {
     // Note it's the job of the selector to tell the TaskQueueManager if
     // a DoWork needs posting.
     main_thread_only().task_queue_manager->selector_.EnableQueue(this);
   } else {
     main_thread_only().task_queue_manager->selector_.DisableQueue(this);
   }
 }
 
 bool TaskQueueImpl::IsQueueEnabled() const {
   return main_thread_only().is_enabled;
 }
 
 bool TaskQueueImpl::IsEmpty() const {
   if (!main_thread_only().delayed_work_queue->Empty() ||
-      !main_thread_only().delayed_incoming_queue.empty() ||
       !main_thread_only().immediate_work_queue->Empty()) {
     return false;
   }
 
   base::AutoLock lock(any_thread_lock_);
-  return any_thread().immediate_incoming_queue.empty();
+  return any_thread().immediate_incoming_queue.empty() &&
+         main_thread_only().delayed_incoming_queue.empty();
 }
 
 bool TaskQueueImpl::HasPendingImmediateWork() const {
   // Any work queue tasks count as immediate work.
   if (!main_thread_only().delayed_work_queue->Empty() ||
       !main_thread_only().immediate_work_queue->Empty()) {
     return true;
   }
 
   // Tasks on |delayed_incoming_queue| that could run now, count as
   // immediate work.
   if (!main_thread_only().delayed_incoming_queue.empty() &&
-      main_thread_only().delayed_incoming_queue.top().delayed_run_time <=
+      main_thread_only().delayed_incoming_queue.begin()->delayed_run_time <=
           main_thread_only().time_domain->CreateLazyNow().Now()) {
     return true;
   }
 
   // Finally tasks on |immediate_incoming_queue| count as immediate work.
   base::AutoLock lock(any_thread_lock_);
   return !any_thread().immediate_incoming_queue.empty();
 }
 
 void TaskQueueImpl::MoveReadyDelayedTasksToDelayedWorkQueue(LazyNow* lazy_now) {
-  // Enqueue all delayed tasks that should be running now, skipping any that
-  // have been canceled.
+  // Enqueue all delayed tasks that should be running now.
   while (!main_thread_only().delayed_incoming_queue.empty()) {
+    DelayedRunTimeQueue::iterator next_task =
+        main_thread_only().delayed_incoming_queue.begin();
+    if (next_task->delayed_run_time > lazy_now->Now())
+      break;
     // TODO(alexclarke): Use extract() when C++17 is allowed.
-    Task& task =
-        const_cast<Task&>(main_thread_only().delayed_incoming_queue.top());
-    if (task.task.IsCancelled()) {
-      main_thread_only().delayed_incoming_queue.pop();
-      continue;
-    }
-    if (task.delayed_run_time > lazy_now->Now())
-      break;
+    Task& task = const_cast<Task&>(*next_task);
     task.set_enqueue_order(
         main_thread_only().task_queue_manager->GetNextSequenceNumber());
     main_thread_only().delayed_work_queue->Push(std::move(task));
-    main_thread_only().delayed_incoming_queue.pop();
+    main_thread_only().delayed_incoming_queue.erase(next_task);
   }
 }
 
-bool TaskQueueImpl::MaybeUpdateImmediateWorkQueues() {
+void TaskQueueImpl::UpdateDelayedWorkQueue(LazyNow* lazy_now) {
   if (!main_thread_only().task_queue_manager)
-    return false;
+    return;
+  MoveReadyDelayedTasksToDelayedWorkQueue(lazy_now);
+  TraceQueueSize(false);
+}
 
-  if (!main_thread_only().immediate_work_queue->Empty())
-    return true;
+void TaskQueueImpl::UpdateImmediateWorkQueue() {
+  DCHECK(main_thread_only().immediate_work_queue->Empty());
+  base::AutoLock lock(any_thread_lock_);
+  if (!main_thread_only().task_queue_manager)
+    return;
 
-  base::AutoLock lock(any_thread_lock_);
   main_thread_only().immediate_work_queue->SwapLocked(
       any_thread().immediate_incoming_queue);
-  // |immediate_work_queue| is now empty so updates are no longer required.
-  return false;
+
+  // |any_thread().immediate_incoming_queue| is now empty so
+  // TimeDomain::UpdateQueues no longer needs to consider this queue for
+  // reloading.
+  main_thread_only().time_domain->UnregisterAsUpdatableTaskQueue(this);
 }
 
 void TaskQueueImpl::TraceQueueSize(bool is_locked) const {
   bool is_tracing;
   TRACE_EVENT_CATEGORY_GROUP_ENABLED(disabled_by_default_tracing_category_,
                                      &is_tracing);
   if (!is_tracing)
     return;
 
   // It's only safe to access the work queues from the main thread.
@@ skipping 61 matching lines @@
   state->SetInteger("immediate_incoming_queue_size",
                     any_thread().immediate_incoming_queue.size());
   state->SetInteger("delayed_incoming_queue_size",
                     main_thread_only().delayed_incoming_queue.size());
   state->SetInteger("immediate_work_queue_size",
                     main_thread_only().immediate_work_queue->Size());
   state->SetInteger("delayed_work_queue_size",
                     main_thread_only().delayed_work_queue->Size());
   if (!main_thread_only().delayed_incoming_queue.empty()) {
     base::TimeDelta delay_to_next_task =
-        (main_thread_only().delayed_incoming_queue.top().delayed_run_time -
+        (main_thread_only().delayed_incoming_queue.begin()->delayed_run_time -
          main_thread_only().time_domain->CreateLazyNow().Now());
     state->SetDouble("delay_to_next_task_ms",
                      delay_to_next_task.InMillisecondsF());
   }
   if (verbose_tracing_enabled) {
     state->BeginArray("immediate_incoming_queue");
     QueueAsValueInto(any_thread().immediate_incoming_queue, state);
     state->EndArray();
     state->BeginArray("delayed_work_queue");
     main_thread_only().delayed_work_queue->AsValueInto(state);
@@ skipping 82 matching lines @@
   // Tasks posted after this point will have a strictly higher enqueue order
   // and will be blocked from running.
   bool task_unblocked = main_thread_only().immediate_work_queue->InsertFence(
       main_thread_only().current_fence);
   task_unblocked |= main_thread_only().delayed_work_queue->InsertFence(
       main_thread_only().current_fence);
 
   if (!task_unblocked && previous_fence) {
     base::AutoLock lock(any_thread_lock_);
     if (!any_thread().immediate_incoming_queue.empty() &&
-        any_thread().immediate_incoming_queue.front().enqueue_order() >
+        any_thread().immediate_incoming_queue.begin()->enqueue_order() >
             previous_fence &&
-        any_thread().immediate_incoming_queue.front().enqueue_order() <
+        any_thread().immediate_incoming_queue.begin()->enqueue_order() <
             main_thread_only().current_fence) {
       task_unblocked = true;
     }
   }
 
   if (main_thread_only().is_enabled && task_unblocked) {
     main_thread_only().task_queue_manager->MaybeScheduleImmediateWork(
         FROM_HERE);
   }
 }
 
 void TaskQueueImpl::RemoveFence() {
   if (!main_thread_only().task_queue_manager)
     return;
 
   EnqueueOrder previous_fence = main_thread_only().current_fence;
   main_thread_only().current_fence = 0;
 
   bool task_unblocked = main_thread_only().immediate_work_queue->RemoveFence();
   task_unblocked |= main_thread_only().delayed_work_queue->RemoveFence();
 
   if (!task_unblocked && previous_fence) {
     base::AutoLock lock(any_thread_lock_);
     if (!any_thread().immediate_incoming_queue.empty() &&
-        any_thread().immediate_incoming_queue.front().enqueue_order() >
+        any_thread().immediate_incoming_queue.begin()->enqueue_order() >
             previous_fence) {
       task_unblocked = true;
     }
   }
 
   if (main_thread_only().is_enabled && task_unblocked) {
     main_thread_only().task_queue_manager->MaybeScheduleImmediateWork(
         FROM_HERE);
   }
 }
 
 bool TaskQueueImpl::BlockedByFence() const {
   if (!main_thread_only().current_fence)
     return false;
 
   if (!main_thread_only().immediate_work_queue->BlockedByFence() ||
       !main_thread_only().delayed_work_queue->BlockedByFence()) {
     return false;
   }
 
   base::AutoLock lock(any_thread_lock_);
   if (any_thread().immediate_incoming_queue.empty())
     return true;
 
-  return any_thread().immediate_incoming_queue.front().enqueue_order() >
+  return any_thread().immediate_incoming_queue.begin()->enqueue_order() >
          main_thread_only().current_fence;
 }
 
 bool TaskQueueImpl::BlockedByFenceLocked() const {
   if (!main_thread_only().current_fence)
     return false;
 
   if (!main_thread_only().immediate_work_queue->BlockedByFence() ||
       !main_thread_only().delayed_work_queue->BlockedByFence()) {
     return false;
   }
 
   if (any_thread().immediate_incoming_queue.empty())
     return true;
 
-  return any_thread().immediate_incoming_queue.front().enqueue_order() >
+  return any_thread().immediate_incoming_queue.begin()->enqueue_order() >
          main_thread_only().current_fence;
 }
 
 // static
-void TaskQueueImpl::QueueAsValueInto(const std::queue<Task>& queue,
+void TaskQueueImpl::QueueAsValueInto(const ComparatorQueue& queue,
                                      base::trace_event::TracedValue* state) {
-  // Remove const to search |queue| in the destructive manner. Restore the
-  // content from |visited| later.
-  std::queue<Task>* mutable_queue = const_cast<std::queue<Task>*>(&queue);
-  std::queue<Task> visited;
-  while (!mutable_queue->empty()) {
-    TaskAsValueInto(mutable_queue->front(), state);
-    visited.push(std::move(mutable_queue->front()));
-    mutable_queue->pop();
+  for (const Task& task : queue) {
+    TaskAsValueInto(task, state);
   }
-  *mutable_queue = std::move(visited);
 }
 
 // static
-void TaskQueueImpl::QueueAsValueInto(const std::priority_queue<Task>& queue,
+void TaskQueueImpl::QueueAsValueInto(const DelayedRunTimeQueue& queue,
                                      base::trace_event::TracedValue* state) {
-  // Remove const to search |queue| in the destructive manner. Restore the
-  // content from |visited| later.
-  std::priority_queue<Task>* mutable_queue =
-      const_cast<std::priority_queue<Task>*>(&queue);
-  std::priority_queue<Task> visited;
-  while (!mutable_queue->empty()) {
-    TaskAsValueInto(mutable_queue->top(), state);
-    visited.push(std::move(const_cast<Task&>(mutable_queue->top())));
-    mutable_queue->pop();
+  for (const Task& task : queue) {
+    TaskAsValueInto(task, state);
   }
-  *mutable_queue = std::move(visited);
 }
 
 // static
 void TaskQueueImpl::TaskAsValueInto(const Task& task,
                                     base::trace_event::TracedValue* state) {
   state->BeginDictionary();
   state->SetString("posted_from", task.posted_from.ToString());
 #ifndef NDEBUG
   if (task.enqueue_order_set())
     state->SetInteger("enqueue_order", task.enqueue_order());
 #else
   state->SetInteger("enqueue_order", task.enqueue_order());
 #endif
   state->SetInteger("sequence_num", task.sequence_num);
   state->SetBoolean("nestable", task.nestable);
   state->SetBoolean("is_high_res", task.is_high_res);
-  state->SetBoolean("is_cancelled", task.task.IsCancelled());
   state->SetDouble(
       "delayed_run_time",
       (task.delayed_run_time - base::TimeTicks()).InMicroseconds() / 1000.0L);
   state->EndDictionary();
 }
 
 }  // namespace internal
 }  // namespace scheduler
 }  // namespace blink