Move Task Scheduler Single Thread Task Runners to Dedicated Threads

base/task_scheduler/task_scheduler_impl.h

Index: base/task_scheduler/task_scheduler_impl.h
diff --git a/base/task_scheduler/task_scheduler_impl.h b/base/task_scheduler/task_scheduler_impl.h
index 7a083c647fbd47968afb2a7bfb7eb4cd0b4266b9..f22cecdb353a347a38a00fba70eef8c521a7895d 100644
--- a/base/task_scheduler/task_scheduler_impl.h
+++ b/base/task_scheduler/task_scheduler_impl.h
@@ -30,6 +30,7 @@ class SchedulerWorkerPoolParams;
 namespace internal {
 
 class DelayedTaskManager;
+class SchedulerSingleThreadWorkerPoolManager;
 class TaskTracker;
 
 // Default TaskScheduler implementation. This class is thread-safe.
@@ -82,6 +83,9 @@ class BASE_EXPORT TaskSchedulerImpl : public TaskScheduler {
   const WorkerPoolIndexForTraitsCallback worker_pool_index_for_traits_callback_;
   std::vector<std::unique_ptr<SchedulerWorkerPoolImpl>> worker_pools_;
 
+  std::unique_ptr<SchedulerSingleThreadWorkerPoolManager>
+      scheduler_single_thread_worker_pool_manager_;
+
 #if DCHECK_IS_ON()
   // Set once JoinForTesting() has returned.
   AtomicFlag join_for_testing_returned_;