Do not take a MessageLoopForIO in the constructor of TaskTrackerPosix.

base/task_scheduler/task_scheduler_impl.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/task_scheduler/task_scheduler_impl.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/memory/ptr_util.h"
 #include "base/task_scheduler/delayed_task_manager.h"
 #include "base/task_scheduler/scheduler_single_thread_task_runner_manager.h"
 #include "base/task_scheduler/scheduler_worker_pool_params.h"
 #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 {
 
 namespace {
 
 enum EnvironmentType {
   BACKGROUND = 0,
   BACKGROUND_BLOCKING,
   FOREGROUND,
@@ skipping 94 matching lines @@
   return histograms;
 }
 
 int TaskSchedulerImpl::GetMaxConcurrentTasksWithTraitsDeprecated(
     const TaskTraits& traits) const {
   return GetWorkerPoolForTraits(traits)->GetMaxConcurrentTasksDeprecated();
 }
 
 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() {
 #if DCHECK_IS_ON()
   DCHECK(!join_for_testing_returned_.IsSet());
 #endif
   single_thread_task_runner_manager_->JoinForTesting();
   for (const auto& worker_pool : worker_pools_)
     worker_pool->DisallowWorkerDetachmentForTesting();
   for (const auto& worker_pool : worker_pools_)
@@ skipping 15 matching lines @@
   Thread::Options service_thread_options;
   service_thread_options.message_loop_type =
 #if defined(OS_POSIX) && !defined(OS_NACL_SFI)
       MessageLoop::TYPE_IO;
 #else
       MessageLoop::TYPE_DEFAULT;
 #endif
   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_.set_watch_file_descriptor_message_loop(
+      static_cast<MessageLoopForIO*>(service_thread_.message_loop()));
 #endif
 
-  // Instantiate 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_ =
       base::MakeUnique<DelayedTaskManager>(service_thread_.task_runner());
 
   single_thread_task_runner_manager_ =
       MakeUnique<SchedulerSingleThreadTaskRunnerManager>(
-          task_tracker_.get(), delayed_task_manager_.get());
+          &task_tracker_, delayed_task_manager_.get());
   single_thread_task_runner_manager_->Start();
 
   // Callback invoked by workers to re-enqueue a sequence in the appropriate
   // PriorityQueue.
   const SchedulerWorkerPoolImpl::ReEnqueueSequenceCallback
       re_enqueue_sequence_callback =
           Bind(&TaskSchedulerImpl::ReEnqueueSequenceCallback, Unretained(this));
 
   // Order must match the EnvironmentType enum.
   const SchedulerWorkerPoolParams* worker_pool_params[] = {
@@ skipping 13 matching lines @@
 
   // Start worker pools.
   for (int environment_type = 0; environment_type < ENVIRONMENT_COUNT;
        ++environment_type) {
     // Passing pointers to objects owned by |this| to the constructor of
     // SchedulerWorkerPoolImpl is safe because a TaskSchedulerImpl can't be
     // deleted before all its worker pools have been joined.
     worker_pools_[environment_type] = MakeUnique<SchedulerWorkerPoolImpl>(
         name_ + kEnvironmentParams[environment_type].name_suffix,
         kEnvironmentParams[environment_type].priority_hint,
-        re_enqueue_sequence_callback, task_tracker_.get(),
+        re_enqueue_sequence_callback, &task_tracker_,
         delayed_task_manager_.get());
     worker_pools_[environment_type]->Start(
         *worker_pool_params[environment_type]);
   }
 }
 
 SchedulerWorkerPoolImpl* TaskSchedulerImpl::GetWorkerPoolForTraits(
     const TaskTraits& traits) const {
   return worker_pools_[GetEnvironmentIndexForTraits(traits)].get();
 }
 
 void TaskSchedulerImpl::ReEnqueueSequenceCallback(
     scoped_refptr<Sequence> sequence) {
   DCHECK(sequence);
 
   const SequenceSortKey sort_key = sequence->GetSortKey();
 
   // The next task in |sequence| should run in a worker pool suited for its
   // traits, except for the priority which is adjusted to the highest priority
   // in |sequence|.
   const TaskTraits traits =
       sequence->PeekTaskTraits().WithPriority(sort_key.priority());
 
   GetWorkerPoolForTraits(traits)->ReEnqueueSequence(std::move(sequence),
                                                     sort_key);
 }
 
 }  // namespace internal
 }  // namespace base