Support FileDescriptorWatcher in TaskScheduler.

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 9fea54a45153cf1c8377e79001f667f85c2b1967..02697bb5d142ba832ac913e9b346827f9a34c8b7 100644
--- a/base/task_scheduler/task_scheduler_impl.h
+++ b/base/task_scheduler/task_scheduler_impl.h
@@ -18,11 +18,9 @@
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/atomic_flag.h"
 #include "base/task_runner.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"
-#include "base/task_scheduler/task_tracker.h"
 #include "base/task_scheduler/task_traits.h"
 #include "base/threading/thread.h"
 
@@ -32,7 +30,9 @@ class SchedulerWorkerPoolParams;
 
 namespace internal {
 
+class DelayedTaskManager;
 class SchedulerServiceThread;
+class TaskTracker;
 
 // Default TaskScheduler implementation. This class is thread-safe.
 class BASE_EXPORT TaskSchedulerImpl : public TaskScheduler {
@@ -79,8 +79,8 @@ class BASE_EXPORT TaskSchedulerImpl : public TaskScheduler {
   // worker pops a Task from it.
   void ReEnqueueSequenceCallback(scoped_refptr<Sequence> sequence);
 
-  TaskTracker task_tracker_;
   Thread service_thread_;
+  std::unique_ptr<TaskTracker> task_tracker_;
   std::unique_ptr<DelayedTaskManager> delayed_task_manager_;
   const WorkerPoolIndexForTraitsCallback worker_pool_index_for_traits_callback_;
   std::vector<std::unique_ptr<SchedulerWorkerPoolImpl>> worker_pools_;