Have content/ create and destroy its own threads.

chrome/browser/chrome_browser_parts_aura.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_CHROME_BROWSER_PARTS_AURA_H_
 #define CHROME_BROWSER_CHROME_BROWSER_PARTS_AURA_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "content/public/browser/browser_main_parts.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace content {
+class IOThreadDelegate;
+}
 
 class ChromeBrowserPartsAura : public content::BrowserMainParts {
  public:
   ChromeBrowserPartsAura();
 
   virtual void PreEarlyInitialization() OVERRIDE;
   virtual void PostEarlyInitialization() OVERRIDE;
   virtual void ToolkitInitialized() OVERRIDE;
   virtual void PreMainMessageLoopStart() OVERRIDE;
   virtual void PostMainMessageLoopStart() OVERRIDE;
-  virtual void PreMainMessageLoopRun() OVERRIDE;
+  virtual content::IOThreadDelegate* PreMainMessageLoopRun() OVERRIDE;
+  virtual void PreMainMessageLoopRunThreadsCreated() OVERRIDE {}
   virtual bool MainMessageLoopRun(int* result_code) OVERRIDE;
   virtual void PostMainMessageLoopRun() OVERRIDE;
+  virtual void PreStopThread(BrowserThread::ID identifier) OVERRIDE {}
+  virtual void PostStopThread(BrowserThread::ID identifier) OVERRIDE {}
+  virtual void FinalCleanup() OVERRIDE {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserPartsAura);
 };
 
 #endif  // CHROME_BROWSER_CHROME_BROWSER_PARTS_AURA_H_