[scheduler] Remove WebThreadImplForUtilityThread from public API.

third_party/WebKit/public/platform/scheduler/child/webthread_base.h

 // 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.
 
 #ifndef THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_CHILD_WEBTHREAD_BASE_H_
 #define THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_CHILD_WEBTHREAD_BASE_H_
 
 #include <map>
 #include <memory>
 
@@ skipping 10 matching lines @@
 // TODO(scheduler-dev): Do not expose this class in Blink public API.
 class BLINK_PLATFORM_EXPORT WebThreadBase : public WebThread {
  public:
   ~WebThreadBase() override;
 
   static std::unique_ptr<WebThreadBase> CreateWorkerThread(
       const char* name,
       base::Thread::Options options);
   static std::unique_ptr<WebThreadBase> CreateCompositorThread(
       base::Thread::Options options);
+  // Must be called on utility thread.
+  static std::unique_ptr<WebThreadBase> InitializeUtilityThread();
 
   // WebThread implementation.
   bool IsCurrentThread() const override;
   PlatformThreadId ThreadId() const override = 0;
 
   virtual void PostIdleTask(const WebTraceLocation& location,
                             IdleTask* idle_task);
 
   void AddTaskObserver(TaskObserver* observer) override;
   void RemoveTaskObserver(TaskObserver* observer) override;
@@ skipping 30 matching lines @@
 
  private:
   typedef std::map<TaskObserver*, TaskObserverAdapter*> TaskObserverMap;
   TaskObserverMap task_observer_map_;
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_CHILD_WEBTHREAD_BASE_H_