Have content/ create and destroy its own threads.

chrome/browser/io_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 CHROME_BROWSER_IO_THREAD_H_
 #define CHROME_BROWSER_IO_THREAD_H_
 #pragma once
 
 #include <string>
 
@@ skipping 31 matching lines @@
 class OriginBoundCertService;
 class ProxyConfigService;
 class ProxyService;
 class SdchManager;
 class SSLConfigService;
 class URLRequestContext;
 class URLRequestContextGetter;
 class URLSecurityManager;
 }  // namespace net
 
-class IOThread : public content::BrowserProcessSubThread {
+// Contains state associated with, and primarily used on, the IO
+// thread.  Also acts as a convenience accessor to the Thread object
+// for the IO thread.
+class IOThread {
  public:
   struct Globals {
     Globals();
     ~Globals();
 
     struct MediaGlobals {
       MediaGlobals();
       ~MediaGlobals();
       // MediaInternals singleton used to aggregate media information.
       scoped_ptr<MediaInternals> media_internals;
@@ skipping 45 matching lines @@
   ChromeNetLog* net_log();
 
   // Returns a getter for the URLRequestContext.  Only called on the UI thread.
   net::URLRequestContextGetter* system_url_request_context_getter();
 
   // Clears the host cache.  Intended to be used to prevent exposing recently
   // visited sites on about:net-internals/#dns and about:dns pages.  Must be
   // called on the IO thread.
   void ClearHostCache();
 
+  // Convenience method similar to base::Thread, giving access to the
+  // actual IO thread.
+  // TODO(joi): Remove this in follow-up changes.
+  MessageLoop* message_loop() const;
+
  protected:
   virtual void Init();
   virtual void CleanUp();
 
  private:
   // Provide SystemURLRequestContextGetter with access to
   // InitSystemRequestContext().
   friend class SystemURLRequestContextGetter;
 
   static void RegisterPrefs(PrefService* local_state);
@@ skipping 56 matching lines @@
       system_url_request_context_getter_;
 
   net::SdchManager* sdch_manager_;
 
   ScopedRunnableMethodFactory<IOThread> method_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(IOThread);
 };
 
 #endif  // CHROME_BROWSER_IO_THREAD_H_