TaskScheduler: Avoid Sequence refcount bump in GetWork()

base/task_scheduler/scheduler_thread_pool.h

 // 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.
 
 #ifndef BASE_TASK_SCHEDULER_SCHEDULER_THREAD_POOL_H_
 #define BASE_TASK_SCHEDULER_SCHEDULER_THREAD_POOL_H_
 
 #include <memory>
 
 #include "base/base_export.h"
 #include "base/memory/ref_counted.h"
 #include "base/task_runner.h"
 #include "base/task_scheduler/sequence.h"
 #include "base/task_scheduler/task.h"
 #include "base/task_scheduler/task_traits.h"
 
 namespace base {
 namespace internal {
 
 class SchedulerWorkerThread;
-struct SequenceSortKey;
+class SequenceSortKey;
 
 // Interface for a thread pool.
 class BASE_EXPORT SchedulerThreadPool {
  public:
   virtual ~SchedulerThreadPool() = default;
 
   // Returns a TaskRunner whose PostTask invocations will result in scheduling
   // Tasks with |traits| and |execution_mode| in this thread pool.
   virtual scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(
       const TaskTraits& traits,
@@ skipping 21 matching lines @@
   virtual void PostTaskWithSequenceNow(
       std::unique_ptr<Task> task,
       scoped_refptr<Sequence> sequence,
       SchedulerWorkerThread* worker_thread) = 0;
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_SCHEDULER_THREAD_POOL_H_