Do not take a MessageLoopForIO in the constructor of TaskTrackerPosix.

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 70c80054f621a398707331e8d12d8a07fd8c751f..871e1be11d7e883a6956405f3aa52bedbd5ea06e 100644
--- a/base/task_scheduler/task_scheduler_impl.cc
+++ b/base/task_scheduler/task_scheduler_impl.cc
@@ -15,11 +15,6 @@
 #include "base/task_scheduler/sequence_sort_key.h"
 #include "base/task_scheduler/task.h"
 #include "base/task_scheduler/task_tracker.h"
-#include "build/build_config.h"
-
-#if defined(OS_POSIX) && !defined(OS_NACL_SFI)
-#include "base/task_scheduler/task_tracker_posix.h"
-#endif
 
 namespace base {
 namespace internal {
@@ -134,13 +129,11 @@ int TaskSchedulerImpl::GetMaxConcurrentTasksWithTraitsDeprecated(
 
 void TaskSchedulerImpl::Shutdown() {
   // TODO(fdoray): Increase the priority of BACKGROUND tasks blocking shutdown.
-  DCHECK(task_tracker_);
-  task_tracker_->Shutdown();
+  task_tracker_.Shutdown();
 }
 
 void TaskSchedulerImpl::FlushForTesting() {
-  DCHECK(task_tracker_);
-  task_tracker_->Flush();
+  task_tracker_.Flush();
 }
 
 void TaskSchedulerImpl::JoinForTesting() {
@@ -176,23 +169,19 @@ void TaskSchedulerImpl::Initialize(
   service_thread_options.timer_slack = TIMER_SLACK_MAXIMUM;
   CHECK(service_thread_.StartWithOptions(service_thread_options));
 
-  // Instantiate TaskTracker. Needs to happen after starting the service thread
-  // to get its message_loop().
-  task_tracker_ =
 #if defined(OS_POSIX) && !defined(OS_NACL_SFI)
-      base::MakeUnique<TaskTrackerPosix>(
-          static_cast<MessageLoopForIO*>(service_thread_.message_loop()));
-#else
-      base::MakeUnique<TaskTracker>();
+  // Needs to happen after starting the service thread to get its
+  // message_loop().
+  task_tracker_.Start(
+      static_cast<MessageLoopForIO*>(service_thread_.message_loop()));
 #endif

[gab, 2017/04/12 19:17:34]

Hmmm, not starting non-POSIX TaskTracker too??

[fdoray, 2017/04/13 12:29:08]

Renamed Start() -> set_watch_file_descriptor_message_loop() to make it clearer
that Start() isn't required with non-POSIX TaskTracker.

 
-  // Start DelayedTaskManager. Needs to happen after starting the service thread
-  // to get its task_runner().
+  // Needs to happen after starting the service thread to get its task_runner().
   delayed_task_manager_.Start(service_thread_.task_runner());
 
   single_thread_task_runner_manager_ =
       MakeUnique<SchedulerSingleThreadTaskRunnerManager>(
-          task_tracker_.get(), &delayed_task_manager_);
+          &task_tracker_, &delayed_task_manager_);
   single_thread_task_runner_manager_->Start();
 
   // Callback invoked by workers to re-enqueue a sequence in the appropriate
@@ -226,8 +215,7 @@ void TaskSchedulerImpl::Initialize(
     worker_pools_[environment_type] = MakeUnique<SchedulerWorkerPoolImpl>(
         name_ + kEnvironmentParams[environment_type].name_suffix,
         kEnvironmentParams[environment_type].priority_hint,
-        re_enqueue_sequence_callback, task_tracker_.get(),
-        &delayed_task_manager_);
+        re_enqueue_sequence_callback, &task_tracker_, &delayed_task_manager_);
     worker_pools_[environment_type]->Start(
         *worker_pool_params[environment_type]);
   }