Separate the create and start phases in DelayedTaskManager.

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 342d5df429889dbf5fccb0d7f828405141c0d8c3..7791b4656db8af0430003161574271ddbcc453a6 100644
--- a/base/task_scheduler/task_scheduler_impl.h
+++ b/base/task_scheduler/task_scheduler_impl.h
@@ -14,6 +14,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/atomic_flag.h"
+#include "base/task_scheduler/delayed_task_manager.h"
 #include "base/task_scheduler/scheduler_worker_pool_impl.h"
 #include "base/task_scheduler/sequence.h"
 #include "base/task_scheduler/task_scheduler.h"
@@ -27,7 +28,6 @@ class HistogramBase;
 
 namespace internal {
 
-class DelayedTaskManager;
 class SchedulerSingleThreadTaskRunnerManager;
 class TaskTracker;
 
@@ -85,7 +85,7 @@ class BASE_EXPORT TaskSchedulerImpl : public TaskScheduler {
   const std::string name_;
   Thread service_thread_;
   std::unique_ptr<TaskTracker> task_tracker_;
-  std::unique_ptr<DelayedTaskManager> delayed_task_manager_;
+  DelayedTaskManager delayed_task_manager_;
   std::unique_ptr<SchedulerSingleThreadTaskRunnerManager>
       single_thread_task_runner_manager_;
   std::unique_ptr<SchedulerWorkerPoolImpl> worker_pools_[4];