Adds a SHUTDOWN_TASK_QUEUE and a PreShutdown api to the scheduler.

components/scheduler/child/web_scheduler_impl.cc

 // Copyright 2015 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/web_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/single_thread_task_runner.h"
 #include "components/scheduler/child/worker_scheduler.h"
 #include "third_party/WebKit/public/platform/WebTraceLocation.h"
 
 namespace scheduler {
 
 WebSchedulerImpl::WebSchedulerImpl(
     ChildScheduler* child_scheduler,
     scoped_refptr<SingleThreadIdleTaskRunner> idle_task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> loading_task_runner,
-    scoped_refptr<base::SingleThreadTaskRunner> timer_task_runner)
+    scoped_refptr<base::SingleThreadTaskRunner> timer_task_runner,
+    scoped_refptr<base::SingleThreadTaskRunner> shutdown_task_runner)
     : child_scheduler_(child_scheduler),
       idle_task_runner_(idle_task_runner),
       loading_task_runner_(loading_task_runner),
-      timer_task_runner_(timer_task_runner) {
+      timer_task_runner_(timer_task_runner),
+      shutdown_task_runner_(shutdown_task_runner) {
 }
 
 WebSchedulerImpl::~WebSchedulerImpl() {
 }
 
 bool WebSchedulerImpl::shouldYieldForHighPriorityWork() {
   return child_scheduler_->ShouldYieldForHighPriorityWork();
 }
 
 bool WebSchedulerImpl::canExceedIdleDeadlineIfRequired() {
@@ skipping 64 matching lines @@
   scoped_ptr<blink::WebThread::Task> scoped_task(task);
   tracked_objects::Location location(web_location.functionName(),
                                      web_location.fileName(), -1, nullptr);
   // Timer tasks should not run in a nested messageloop.
   timer_task_runner_->PostNonNestableDelayedTask(
       location,
       base::Bind(&WebSchedulerImpl::runTask, base::Passed(&scoped_task)),
       base::TimeDelta::FromMilliseconds(delayMs));
 }
 
+void WebSchedulerImpl::postShutdownTask(
+    const blink::WebTraceLocation& web_location,
+    blink::WebThread::Task* task,
+    long long delayMs) {
+  DCHECK(shutdown_task_runner_);
+  scoped_ptr<blink::WebThread::Task> scoped_task(task);
+  tracked_objects::Location location(web_location.functionName(),
+                                     web_location.fileName(), -1, nullptr);
+  shutdown_task_runner_->PostDelayedTask(
+      location,
+      base::Bind(&WebSchedulerImpl::runTask, base::Passed(&scoped_task)),
+      base::TimeDelta::FromMilliseconds(delayMs));
+}
+
+void WebSchedulerImpl::preShutdown() {
+  child_scheduler_->PreShutdown();
+}
+
 }  // namespace scheduler