Support FileDescriptorWatcher in TaskScheduler.

base/task_scheduler/task_tracker.cc

Index: base/task_scheduler/task_tracker.cc
diff --git a/base/task_scheduler/task_tracker.cc b/base/task_scheduler/task_tracker.cc
index be54614bec03fc63c555e8435cf62c529f642904..90c52937747ea459761ad8b972b6f4b2c6e2b8a7 100644
--- a/base/task_scheduler/task_tracker.cc
+++ b/base/task_scheduler/task_tracker.cc
@@ -213,6 +213,7 @@ bool TaskTracker::RunTask(std::unique_ptr<Task> task,
   const TaskShutdownBehavior shutdown_behavior =
       task->traits.shutdown_behavior();
   const bool can_run_task = BeforeRunTask(shutdown_behavior);
+  const bool is_delayed = !task->delayed_run_time.is_null();
 
   if (can_run_task) {
     // All tasks run through here and the scheduler itself doesn't use
@@ -254,14 +255,13 @@ bool TaskTracker::RunTask(std::unique_ptr<Task> task,
                    MakeUnique<TaskTracingInfo>(task->traits, execution_mode,
                                                sequence_token));
 
-      debug::TaskAnnotator task_annotator;
-      task_annotator.RunTask(kQueueFunctionName, task.get());
+      PerformRunTask(std::move(task));
     }
 
     AfterRunTask(shutdown_behavior);
   }
 
-  if (task->delayed_run_time.is_null())
+  if (!is_delayed)
     DecrementNumPendingUndelayedTasks();
 
   return can_run_task;
@@ -280,6 +280,10 @@ void TaskTracker::SetHasShutdownStartedForTesting() {
   state_->StartShutdown();
 }
 
+void TaskTracker::PerformRunTask(std::unique_ptr<Task> task) {
+  debug::TaskAnnotator().RunTask(kQueueFunctionName, task.get());

[gab, 2016/10/21 16:10:48]

Actually this makes me realize that I'm not sure it is/was correct to
instantiates a new TaskAnnotator every time..

Not a blocker for this CL because this was already the case but worth looking
into.

[fdoray, 2016/10/27 13:06:50]

Yes, it's wrong to initialize a TaskAnnotator every time. I plan to fix this in
a separate CL.

+}
+
 void TaskTracker::PerformShutdown() {
   {
     AutoSchedulerLock auto_lock(shutdown_lock_);