Adds a SHUTDOWN_TASK_QUEUE and a PreShutdown api to the scheduler.

components/scheduler/child/worker_scheduler_impl.cc

 // Copyright 2014 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 "components/scheduler/child/worker_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
@@ skipping 30 matching lines @@
   DCHECK(initialized_);
   return helper_.DefaultTaskRunner();
 }
 
 scoped_refptr<SingleThreadIdleTaskRunner>
 WorkerSchedulerImpl::IdleTaskRunner() {
   DCHECK(initialized_);
   return helper_.IdleTaskRunner();
 }
 
+scoped_refptr<base::SingleThreadTaskRunner>
+WorkerSchedulerImpl::ShutdownTaskRunner() {
+  DCHECK(initialized_);
+  return helper_.ShutdownTaskRunner();
+}
+
 bool WorkerSchedulerImpl::CanExceedIdleDeadlineIfRequired() const {
   DCHECK(initialized_);
   return helper_.CanExceedIdleDeadlineIfRequired();
 }
 
 bool WorkerSchedulerImpl::ShouldYieldForHighPriorityWork() {
   // We don't consider any work as being high priority on workers.
   return false;
 }
 
 void WorkerSchedulerImpl::AddTaskObserver(
     base::MessageLoop::TaskObserver* task_observer) {
   DCHECK(initialized_);
   helper_.AddTaskObserver(task_observer);
 }
 
 void WorkerSchedulerImpl::RemoveTaskObserver(
     base::MessageLoop::TaskObserver* task_observer) {
   DCHECK(initialized_);
   helper_.RemoveTaskObserver(task_observer);
 }
 
+void WorkerSchedulerImpl::PreShutdown() {
+  DCHECK(initialized_);
+  helper_.PreShutdown();
+}
+
 void WorkerSchedulerImpl::Shutdown() {
   DCHECK(initialized_);
   helper_.Shutdown();
 }
 
 SchedulerHelper* WorkerSchedulerImpl::GetSchedulerHelperForTesting() {
   return &helper_;
 }
 
 bool WorkerSchedulerImpl::CanEnterLongIdlePeriod(base::TimeTicks,
                                                  base::TimeDelta*) {
   return true;
 }
 
 base::TimeTicks WorkerSchedulerImpl::CurrentIdleTaskDeadlineForTesting() const {
   base::TimeTicks deadline;
   helper_.CurrentIdleTaskDeadlineCallback(&deadline);
   return deadline;
 }
 
 }  // namespace scheduler