[renderer]: Fix RendererScheduler shutdown logic to ensure it is shutdown before the MessageLoop.

content/renderer/scheduler/web_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 "content/renderer/scheduler/web_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/single_thread_task_runner.h"
 #include "content/renderer/scheduler/renderer_scheduler.h"
 #include "third_party/WebKit/public/platform/WebTraceLocation.h"
@@ skipping 63 matching lines @@
   DCHECK(loading_task_runner_);
   scoped_ptr<blink::WebThread::Task> scoped_task(task);
   tracked_objects::Location location(web_location.functionName(),
                                      web_location.fileName(), -1, nullptr);
   loading_task_runner_->PostTask(
       location,
       base::Bind(&WebSchedulerImpl::runTask, base::Passed(&scoped_task)));
 }
 
 void WebSchedulerImpl::shutdown() {
-  idle_task_runner_ = nullptr;
-  loading_task_runner_ = nullptr;
-  return renderer_scheduler_->Shutdown();
+  // TODO(rmcilroy): Delete this method once the blink side is removed.
 }
 
 }  // namespace content