Remove WorkerThreadScheduler::default_task_runner_

This CL is a pure refactoring.

Change-Id: Ic3b03be80e1e2e5071c5bfc95e2212214a5af183
Reviewed-on: https://chromium-review.googlesource.com/1094819Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Yuta Kitamura <yutak@chromium.org>
Commit-Queue: Hajime Hoshi <hajimehoshi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566799}

third_party/blink/renderer/platform/scheduler/worker/worker_thread_scheduler.cc

@@ -114,10 +114,7 @@ WorkerThreadScheduler::WorkerThreadScheduler(
                     kUnspecifiedWorkerThreadLoadTrackerReportingInterval),
       lifecycle_state_(proxy ? proxy->lifecycle_state()
                              : SchedulingLifecycleState::kNotThrottled),
-      worker_metrics_helper_(thread_type),
-      default_task_runner_(TaskQueueWithTaskType::Create(
-          helper()->DefaultNonMainThreadTaskQueue(),
-          TaskType::kWorkerThreadTaskQueueDefault)) {
+      worker_metrics_helper_(thread_type) {
   thread_start_time_ = helper()->NowTicks();
   load_tracker_.Resume(thread_start_time_);
   helper()->AddTaskTimeObserver(this);
@@ -145,7 +142,8 @@ WorkerThreadScheduler::~WorkerThreadScheduler() {
 
 scoped_refptr<base::SingleThreadTaskRunner>
 WorkerThreadScheduler::DefaultTaskRunner() {
-  return default_task_runner_;
+  NOTREACHED();
+  return nullptr;
 }
 
 scoped_refptr<SingleThreadIdleTaskRunner>

third_party/blink/renderer/platform/scheduler/worker/worker_thread_scheduler.h

@@ -133,8 +133,6 @@ class PLATFORM_EXPORT WorkerThreadScheduler
 
   WorkerMetricsHelper worker_metrics_helper_;
 
-  scoped_refptr<base::SingleThreadTaskRunner> default_task_runner_;
-
   // This controller should be initialized before any TraceableVariables
   // because they require one to initialize themselves.
   TraceableVariableController traceable_variable_controller_;

third_party/blink/renderer/platform/scheduler/worker/worker_thread_scheduler_unittest.cc

@@ -113,7 +113,7 @@ class WorkerThreadSchedulerTest : public testing::Test {
 
   void Init() {
     scheduler_->Init();
-    default_task_runner_ = scheduler_->DefaultTaskRunner();
+    default_task_runner_ = scheduler_->CreateTaskRunner();
     idle_task_runner_ = scheduler_->IdleTaskRunner();
     timeline_ = nullptr;
   }
@@ -404,6 +404,6 @@ TEST_F(WorkerThreadSchedulerTest, TestLongIdlePeriodTimeline) {
   EXPECT_THAT(timeline, ElementsAreArray(expected_timeline));
 }
 
-}  // namespace worker_scheduler_impl_unittest
+}  // namespace worker_thread_scheduler_unittest
 }  // namespace scheduler
 }  // namespace blink