Replace base::Callback with base::OnceCallback in base::PendingTask

base/task_scheduler/sequence.cc

 // Copyright 2016 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 "base/task_scheduler/sequence.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/time/time.h"
 
 namespace base {
 namespace internal {
 
 Sequence::Sequence() = default;
 
 bool Sequence::PushTask(std::unique_ptr<Task> task) {
   DCHECK(task->sequenced_time.is_null());
   task->sequenced_time = base::TimeTicks::Now();
 
   AutoSchedulerLock auto_lock(lock_);
   ++num_tasks_per_priority_[static_cast<int>(task->traits.priority())];
   queue_.push(std::move(task));
 
   // Return true if the sequence was empty before the push.
   return queue_.size() == 1;
 }
 
-const Task* Sequence::PeekTask() const {
+Task* Sequence::PeekTask() const {
   AutoSchedulerLock auto_lock(lock_);
 
   if (queue_.empty())
     return nullptr;
 
   return queue_.front().get();
 }
 
 bool Sequence::PopTask() {
   // Delete the popped task outside the scope of |lock_|. This prevents a double
@@ skipping 41 matching lines @@
     next_task_sequenced_time = queue_.front()->sequenced_time;
   }
 
   return SequenceSortKey(priority, next_task_sequenced_time);
 }
 
 Sequence::~Sequence() = default;
 
 }  // namespace internal
 }  // namespace base