Adds a SHUTDOWN_TASK_QUEUE and a PreShutdown api to the scheduler.

mojo/services/html_viewer/web_scheduler_impl.cc

Index: mojo/services/html_viewer/web_scheduler_impl.cc
diff --git a/mojo/services/html_viewer/web_scheduler_impl.cc b/mojo/services/html_viewer/web_scheduler_impl.cc
index c0dbc93cb03492dc59e79cd777b512a4ebfd3304..e0ef1cdfacbc3bec327385a946dee006e3cabe6f 100644
--- a/mojo/services/html_viewer/web_scheduler_impl.cc
+++ b/mojo/services/html_viewer/web_scheduler_impl.cc
@@ -46,12 +46,29 @@ void WebSchedulerImpl::postTimerTask(
   scoped_ptr<blink::WebThread::Task> scoped_task(task);
   tracked_objects::Location location(web_location.functionName(),
                                      web_location.fileName(), -1, nullptr);
-  task_runner_->PostDelayedTask(
+  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) {
+  scoped_ptr<blink::WebThread::Task> scoped_task(task);
+  tracked_objects::Location location(web_location.functionName(),
+                                     web_location.fileName(), -1, nullptr);
+  task_runner_->PostNonNestableDelayedTask(
+      location,
+      base::Bind(&WebSchedulerImpl::RunTask, base::Passed(&scoped_task)),
+      base::TimeDelta::FromMilliseconds(delayMs));
+}
+
+void WebSchedulerImpl::preShutdown() {
+  // TODO(alexclarke) Implement pre shutdown for mojo?

[sky, 2015/04/23 16:35:37]

Add a NOTIMPLEMENTED here.

[alex clarke (OOO till 29th), 2015/04/23 17:34:32]

Done.

+}
+
 // static
 void WebSchedulerImpl::RunIdleTask(
     scoped_ptr<blink::WebThread::IdleTask> task) {