[scheduler] Remove WebThreadImplForUtilityThread from public API.

content/utility/utility_blink_platform_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 "content/utility/utility_blink_platform_impl.h"
 
-#include "third_party/WebKit/public/platform/scheduler/utility/webthread_impl_for_utility_thread.h"
+#include "third_party/WebKit/public/platform/scheduler/child/webthread_base.h"
 
 namespace content {
 
 UtilityBlinkPlatformImpl::UtilityBlinkPlatformImpl()
-    : main_thread_(new blink::scheduler::WebThreadImplForUtilityThread()) {}
+    : main_thread_(blink::scheduler::WebThreadBase::InitializeUtilityThread()) {
+}
 
 UtilityBlinkPlatformImpl::~UtilityBlinkPlatformImpl() {
 }
 
 blink::WebThread* UtilityBlinkPlatformImpl::CurrentThread() {
   if (main_thread_->IsCurrentThread())
     return main_thread_.get();
   return BlinkPlatformImpl::CurrentThread();
 }
 
 }  // namespace content