TaskScheduler: Nits in service thread and delayed tasks code.

base/task_scheduler/task_scheduler_impl.cc

Index: base/task_scheduler/task_scheduler_impl.cc
diff --git a/base/task_scheduler/task_scheduler_impl.cc b/base/task_scheduler/task_scheduler_impl.cc
index a3fc0d3830b99086093df55a4acab424195b921f..4a1feb13ef3103405dc2c8a87b6f1caccb9f4a48 100644
--- a/base/task_scheduler/task_scheduler_impl.cc
+++ b/base/task_scheduler/task_scheduler_impl.cc
@@ -84,7 +84,8 @@ void TaskSchedulerImpl::Initialize(
     const std::vector<SchedulerWorkerPoolParams>& worker_pool_params_vector) {
   DCHECK(!worker_pool_params_vector.empty());
 
-  // Start the service thread.
+  // Start the service thread. On POSIX, the service thread runs a
+  // MessageLoopForIO to support FileDescriptorWatcher.
   constexpr MessageLoop::Type kServiceThreadMessageLoopType =
 #if defined(OS_POSIX)
       MessageLoop::TYPE_IO;
@@ -95,15 +96,15 @@ void TaskSchedulerImpl::Initialize(
   CHECK(service_thread_.StartWithOptions(
       Thread::Options(kServiceThreadMessageLoopType, kDefaultStackSize)));
 
-  const SchedulerWorkerPoolImpl::ReEnqueueSequenceCallback
-      re_enqueue_sequence_callback =
-          Bind(&TaskSchedulerImpl::ReEnqueueSequenceCallback, Unretained(this));
-
   // Instantiate the DelayedTaskManager. The service thread must be started
   // before its TaskRunner is available.
   delayed_task_manager_ =
       base::MakeUnique<DelayedTaskManager>(service_thread_.task_runner());
 
+  const SchedulerWorkerPoolImpl::ReEnqueueSequenceCallback

[robliao, 2016/10/18 20:21:43]

What the motivation for this reordering?

[gab, 2016/10/18 20:50:40]

It's only required below and |delayed_task_manager| is related to
|service_thread_| created before it so both this being here makes sense and
|delayed_task_manager|'s init moving up.

+      re_enqueue_sequence_callback =
+          Bind(&TaskSchedulerImpl::ReEnqueueSequenceCallback, Unretained(this));
+
   // Start worker pools.
   for (const auto& worker_pool_params : worker_pool_params_vector) {
     // Passing pointers to objects owned by |this| to