Have content/ create and destroy its own threads.

content/browser/browser_process_sub_thread.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_BROWSER_BROWSER_PROCESS_SUB_THREAD_H_
 #define CONTENT_BROWSER_BROWSER_PROCESS_SUB_THREAD_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "content/browser/browser_thread_impl.h"
@@ skipping 13 matching lines @@
 //
 // Applications must initialize the COM library before they can call
 // COM library functions other than CoGetMalloc and memory allocation
 // functions, so this class initializes COM for those users.
 class CONTENT_EXPORT BrowserProcessSubThread : public BrowserThreadImpl {
  public:
   explicit BrowserProcessSubThread(BrowserThread::ID identifier);
   virtual ~BrowserProcessSubThread();
 
  protected:
-  virtual void Init();
-  virtual void CleanUp();
+  virtual void Init() OVERRIDE;
+  virtual void CleanUp() OVERRIDE;
 
  private:
   // Each specialized thread has its own notification service.
   // Note: We don't use scoped_ptr because the destructor runs on the wrong
   // thread.
   NotificationService* notification_service_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserProcessSubThread);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_BROWSER_PROCESS_SUB_THREAD_H_