[base/task] Do not require a SequenceManager in TaskQueueImpl::SweepCancelledTasks.

TaskQueueImpl::SweepCancelledTasks doesn't have to know about
SequenceManager.

R=skyostil@chromium.org,alexclarke@chromium.org

Change-Id: Ifad12c6fe652a323b776066a49aeb6e11f14e515
Reviewed-on: https://chromium-review.googlesource.com/c/1349265Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Commit-Queue: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611819}

base/task/sequence_manager/task_queue_impl.cc

@@ -868,9 +868,7 @@ TaskQueueImpl::CreateQueueEnabledVoter(scoped_refptr<TaskQueue> task_queue) {
 void TaskQueueImpl::SweepCanceledDelayedTasks(TimeTicks now) {
   if (main_thread_only().delayed_incoming_queue.empty())
     return;
-  const SequenceManagerImpl* sequence_manager = sequence_manager_;
-  main_thread_only().delayed_incoming_queue.SweepCancelledTasks(
-      sequence_manager);
+  main_thread_only().delayed_incoming_queue.SweepCancelledTasks();
 
   // Also consider shrinking the work queue if it's wasting memory.
   main_thread_only().delayed_work_queue->MaybeShrinkQueue();
@@ -1057,8 +1055,7 @@ void TaskQueueImpl::DelayedIncomingQueue::pop() {
   queue_.pop();
 }
 
-void TaskQueueImpl::DelayedIncomingQueue::SweepCancelledTasks(
-    const SequenceManagerImpl* sequence_manager) {
+void TaskQueueImpl::DelayedIncomingQueue::SweepCancelledTasks() {
   std::priority_queue<Task> remaining_tasks;
   while (!empty()) {
     if (!top().task.IsCancelled()) {

base/task/sequence_manager/task_queue_impl.h

@@ -285,7 +285,7 @@ class BASE_EXPORT TaskQueueImpl {
       return pending_high_res_tasks_;
     }
 
-    void SweepCancelledTasks(const SequenceManagerImpl*);
+    void SweepCancelledTasks();
     std::priority_queue<Task> TakeTasks() { return std::move(queue_); }
     void AsValueInto(TimeTicks now, trace_event::TracedValue* state) const;