Remove WebScheduler::shutdown() which is no longer needed.

Source/platform/scheduler/Scheduler.cpp

 // 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 "config.h"
 #include "platform/scheduler/Scheduler.h"
 
 #include "public/platform/Platform.h"
 #include "public/platform/WebScheduler.h"
 #include "public/platform/WebTraceLocation.h"
@@ skipping 42 matching lines @@
     s_sharedScheduler = scheduler;
 }
 
 Scheduler::Scheduler(WebScheduler* webScheduler)
     : m_webScheduler(webScheduler)
 {
 }
 
 Scheduler::~Scheduler()
 {
-    if (m_webScheduler)
-        m_webScheduler->shutdown();
 }
 
 void Scheduler::postIdleTask(const WebTraceLocation& location, PassOwnPtr<IdleTask> idleTask)
 {
     if (m_webScheduler)
         m_webScheduler->postIdleTask(location, new IdleTaskRunner(idleTask));
 }
 
 void Scheduler::postNonNestableIdleTask(const WebTraceLocation& location, PassOwnPtr<IdleTask> idleTask)
 {
@@ skipping 14 matching lines @@
 }
 
 bool Scheduler::shouldYieldForHighPriorityWork() const
 {
     if (m_webScheduler)
         return m_webScheduler->shouldYieldForHighPriorityWork();
     return false;
 }
 
 } // namespace blink