TaskScheduler: Replace the SchedulerServiceThread with a base::Thread.

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 af9639b28377a2b531cda549458931fc6de52654..e1718c8733548421d10cb9631284876358b478e0 100644
--- a/base/task_scheduler/task_scheduler_impl.cc
+++ b/base/task_scheduler/task_scheduler_impl.cc
@@ -9,7 +9,6 @@
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/memory/ptr_util.h"
-#include "base/task_scheduler/scheduler_service_thread.h"
 #include "base/task_scheduler/scheduler_worker_pool_params.h"
 #include "base/task_scheduler/sequence_sort_key.h"
 #include "base/task_scheduler/task.h"
@@ -42,7 +41,7 @@ void TaskSchedulerImpl::PostTaskWithTraits(
   // Post |task| as part of a one-off single-task Sequence.
   GetWorkerPoolForTraits(traits)->PostTaskWithSequence(
       MakeUnique<Task>(from_here, task, traits, TimeDelta()),
-      make_scoped_refptr(new Sequence), nullptr);
+      make_scoped_refptr(new Sequence), nullptr, TimeDelta());
 }
 
 scoped_refptr<TaskRunner> TaskSchedulerImpl::CreateTaskRunnerWithTraits(
@@ -65,9 +64,9 @@ void TaskSchedulerImpl::JoinForTesting() {
 #if DCHECK_IS_ON()
   DCHECK(!join_for_testing_returned_.IsSet());
 #endif
+  service_thread_.Stop();

[robliao, 2016/10/12 20:55:45]

What's the motivation for this move?
I would expect the service thread to remain the last thread terminated.

Also, this will destroy any pending delayed tasks. I expect that's okay for
tests, right?

[fdoray, 2016/10/13 13:51:29]

I didn't like the fact that the service thread could recreate a SchedulerWorker
that had already been joined. This is now addressed in a separate CL
https://codereview.chromium.org/2414043002/

   for (const auto& worker_pool : worker_pools_)
     worker_pool->JoinForTesting();
-  service_thread_->JoinForTesting();
 #if DCHECK_IS_ON()
   join_for_testing_returned_.Set();
 #endif
@@ -75,11 +74,9 @@ void TaskSchedulerImpl::JoinForTesting() {
 
 TaskSchedulerImpl::TaskSchedulerImpl(const WorkerPoolIndexForTraitsCallback&
                                          worker_pool_index_for_traits_callback)
-    : delayed_task_manager_(
-          Bind(&TaskSchedulerImpl::OnDelayedRunTimeUpdated, Unretained(this))),
+    : service_thread_("TaskSchedulerServiceThread"),
       worker_pool_index_for_traits_callback_(
-          worker_pool_index_for_traits_callback)
-{
+          worker_pool_index_for_traits_callback) {
   DCHECK(!worker_pool_index_for_traits_callback_.is_null());
 }
 
@@ -87,23 +84,32 @@ void TaskSchedulerImpl::Initialize(
     const std::vector<SchedulerWorkerPoolParams>& worker_pool_params_vector) {
   DCHECK(!worker_pool_params_vector.empty());
 
+  // Start the service thread.
+  constexpr MessageLoop::Type kServiceThreadMessageLoopType =
+#if defined(OS_POSIX)
+      MessageLoop::TYPE_IO;
+#else
+      MessageLoop::TYPE_DEFAULT;
+#endif
+  constexpr size_t kDefaultStackSize = 0;
+  const bool service_thread_start_result = service_thread_.StartWithOptions(

[robliao, 2016/10/12 20:55:45]

Inline this call to the CHECK below.

[fdoray, 2016/10/13 13:51:29]

Done.

+      Thread::Options(kServiceThreadMessageLoopType, kDefaultStackSize));
+  CHECK(service_thread_start_result);
+
   const SchedulerWorkerPoolImpl::ReEnqueueSequenceCallback
       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
     // SchedulerWorkerPoolImpl::Create() is safe because a TaskSchedulerImpl
     // can't be deleted before all its worker pools have been joined.
     worker_pools_.push_back(SchedulerWorkerPoolImpl::Create(
         worker_pool_params, re_enqueue_sequence_callback, &task_tracker_,
-        &delayed_task_manager_));
+        service_thread_.task_runner()));
     CHECK(worker_pools_.back());
   }
-
-  service_thread_ = SchedulerServiceThread::Create(&task_tracker_,
-                                                   &delayed_task_manager_);
-  CHECK(service_thread_);
 }
 
 SchedulerWorkerPool* TaskSchedulerImpl::GetWorkerPoolForTraits(
@@ -129,9 +135,5 @@ void TaskSchedulerImpl::ReEnqueueSequenceCallback(
                                                     sort_key);
 }
 
-void TaskSchedulerImpl::OnDelayedRunTimeUpdated() {
-  service_thread_->WakeUp();
-}
-
 }  // namespace internal
 }  // namespace base