Revert 111695 - Have content/ create and destroy its own threads.

content/public/browser/browser_thread_delegate.h

-// Copyright (c) 2011 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 CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_DELEGATE_H_
-#define CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_DELEGATE_H_
-#pragma once
-
-namespace content {
-
-// A class with this type may be registered via
-// BrowserThread::SetDelegate.
-//
-// If registered as such, it will receive an Init() call right before
-// the BrowserThread in question starts its message loop (and right
-// after the BrowserThread has done its own initialization), and a
-// CleanUp call right after the message loop ends (and before the
-// BrowserThread has done its own clean-up).
-class BrowserThreadDelegate {
- public:
-  virtual ~BrowserThreadDelegate() {}
-
-  // Called just prior to starting the message loop.
-  virtual void Init() = 0;
-
-  // Called just after the message loop ends.
-  virtual void CleanUp() = 0;
-};
-
-}  // namespace content
-
-#endif  // CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_DELEGATE_H_