Adds a SHUTDOWN_TASK_QUEUE and a PreShutdown api to the scheduler.

components/scheduler/renderer/renderer_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/renderer/renderer_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 42 matching lines @@
       TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"), "RendererScheduler",
       this);
 }
 
 RendererSchedulerImpl::~RendererSchedulerImpl() {
   TRACE_EVENT_OBJECT_DELETED_WITH_ID(
       TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"), "RendererScheduler",
       this);
 }
 
+void RendererSchedulerImpl::PreShutdown() {
+  helper_.PreShutdown();
+}
+
 void RendererSchedulerImpl::Shutdown() {
   helper_.Shutdown();
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
 RendererSchedulerImpl::DefaultTaskRunner() {
   return helper_.DefaultTaskRunner();
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
@@ skipping 12 matching lines @@
   helper_.CheckOnValidThread();
   return loading_task_runner_;
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
 RendererSchedulerImpl::TimerTaskRunner() {
   helper_.CheckOnValidThread();
   return timer_task_runner_;
 }
 
+scoped_refptr<base::SingleThreadTaskRunner>
+RendererSchedulerImpl::ShutdownTaskRunner() {
+  helper_.CheckOnValidThread();
+  return helper_.ShutdownTaskRunner();
+}
+
 bool RendererSchedulerImpl::CanExceedIdleDeadlineIfRequired() const {
   return helper_.CanExceedIdleDeadlineIfRequired();
 }
 
 void RendererSchedulerImpl::AddTaskObserver(
     base::MessageLoop::TaskObserver* task_observer) {
   helper_.AddTaskObserver(task_observer);
 }
 
 void RendererSchedulerImpl::RemoveTaskObserver(
@@ skipping 515 matching lines @@
       // meaningful touchstart response and should not impact task priority.
       return current_state;
 
     default:
       break;
   }
   return InputStreamState::ACTIVE;
 }
 
 }  // namespace scheduler