scheduler: Return a base::SingleThreadTaskRunner for the default task runner.

BUG=none

Review URL: https://codereview.chromium.org/1585723002

Cr-Commit-Position: refs/heads/master@{#369408}

components/scheduler/child/child_scheduler.h

@@ -22,8 +22,7 @@ class SCHEDULER_EXPORT ChildScheduler {
   virtual ~ChildScheduler() {}
 
   // Returns the default task runner.
-  // TODO(alexclarke): Change this to return a SingleThreadIdleTaskRunner.
-  virtual scoped_refptr<TaskQueue> DefaultTaskRunner() = 0;
+  virtual scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner() = 0;
 
   // Returns the idle task runner. Tasks posted to this runner may be reordered
   // relative to other task types and may be starved for an arbitrarily long

components/scheduler/child/web_scheduler_impl.cc

@@ -17,7 +17,7 @@ WebSchedulerImpl::WebSchedulerImpl(
     ChildScheduler* child_scheduler,
     scoped_refptr<SingleThreadIdleTaskRunner> idle_task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> loading_task_runner,
-    scoped_refptr<TaskQueue> timer_task_runner)
+    scoped_refptr<base::SingleThreadTaskRunner> timer_task_runner)
     : child_scheduler_(child_scheduler),
       idle_task_runner_(idle_task_runner),
       timer_task_runner_(timer_task_runner),

components/scheduler/child/web_scheduler_impl.h

@@ -29,7 +29,7 @@ class SCHEDULER_EXPORT WebSchedulerImpl : public blink::WebScheduler {
       ChildScheduler* child_scheduler,
       scoped_refptr<SingleThreadIdleTaskRunner> idle_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> loading_task_runner,
-      scoped_refptr<TaskQueue> timer_task_runner);
+      scoped_refptr<base::SingleThreadTaskRunner> timer_task_runner);
   ~WebSchedulerImpl() override;
 
   // blink::WebScheduler implementation:
@@ -58,7 +58,7 @@ class SCHEDULER_EXPORT WebSchedulerImpl : public blink::WebScheduler {
 
   ChildScheduler* child_scheduler_;  // NOT OWNED
   scoped_refptr<SingleThreadIdleTaskRunner> idle_task_runner_;
-  scoped_refptr<TaskQueue> timer_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> timer_task_runner_;
   scoped_ptr<WebTaskRunnerImpl> loading_web_task_runner_;
   scoped_ptr<WebTaskRunnerImpl> timer_web_task_runner_;
 };

components/scheduler/child/worker_scheduler_impl.cc

@@ -39,7 +39,8 @@ void WorkerSchedulerImpl::Init() {
   idle_helper_.EnableLongIdlePeriod();
 }
 
-scoped_refptr<TaskQueue> WorkerSchedulerImpl::DefaultTaskRunner() {
+scoped_refptr<base::SingleThreadTaskRunner>
+WorkerSchedulerImpl::DefaultTaskRunner() {
   DCHECK(initialized_);
   return helper_.DefaultTaskRunner();
 }

components/scheduler/child/worker_scheduler_impl.h

@@ -29,7 +29,7 @@ class SCHEDULER_EXPORT WorkerSchedulerImpl : public WorkerScheduler,
   ~WorkerSchedulerImpl() override;
 
   // WorkerScheduler implementation:
-  scoped_refptr<TaskQueue> DefaultTaskRunner() override;
+  scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner() override;
   scoped_refptr<SingleThreadIdleTaskRunner> IdleTaskRunner() override;
   bool CanExceedIdleDeadlineIfRequired() const override;
   bool ShouldYieldForHighPriorityWork() override;

components/scheduler/renderer/renderer_scheduler_impl.cc

@@ -155,7 +155,8 @@ scoped_ptr<blink::WebThread> RendererSchedulerImpl::CreateMainThread() {
   return make_scoped_ptr(new WebThreadImplForRendererScheduler(this));
 }
 
-scoped_refptr<TaskQueue> RendererSchedulerImpl::DefaultTaskRunner() {
+scoped_refptr<base::SingleThreadTaskRunner>
+RendererSchedulerImpl::DefaultTaskRunner() {
   return helper_.DefaultTaskRunner();
 }
 

components/scheduler/renderer/renderer_scheduler_impl.h

@@ -41,7 +41,7 @@ class SCHEDULER_EXPORT RendererSchedulerImpl
 
   // RendererScheduler implementation:
   scoped_ptr<blink::WebThread> CreateMainThread() override;
-  scoped_refptr<TaskQueue> DefaultTaskRunner() override;
+  scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner() override;
   scoped_refptr<SingleThreadIdleTaskRunner> IdleTaskRunner() override;
   scoped_refptr<base::SingleThreadTaskRunner> CompositorTaskRunner() override;
   scoped_refptr<base::SingleThreadTaskRunner> LoadingTaskRunner() override;

content/test/fake_renderer_scheduler.cc

@@ -18,7 +18,8 @@ scoped_ptr<blink::WebThread> FakeRendererScheduler::CreateMainThread() {
   return nullptr;
 }
 
-scoped_refptr<scheduler::TaskQueue> FakeRendererScheduler::DefaultTaskRunner() {
+scoped_refptr<base::SingleThreadTaskRunner>
+FakeRendererScheduler::DefaultTaskRunner() {
   return nullptr;
 }
 

content/test/fake_renderer_scheduler.h

@@ -17,7 +17,7 @@ class FakeRendererScheduler : public scheduler::RendererScheduler {
 
   // RendererScheduler implementation.
   scoped_ptr<blink::WebThread> CreateMainThread() override;
-  scoped_refptr<scheduler::TaskQueue> DefaultTaskRunner() override;
+  scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner() override;
   scoped_refptr<base::SingleThreadTaskRunner> CompositorTaskRunner() override;
   scoped_refptr<base::SingleThreadTaskRunner> LoadingTaskRunner() override;
   scoped_refptr<scheduler::SingleThreadIdleTaskRunner> IdleTaskRunner()