Have content/ create and destroy its own threads.

chrome/browser/chrome_browser_parts_aura.cc

 // 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.
 
 #include "chrome/browser/chrome_browser_parts_aura.h"
 #include "chrome/browser/ui/views/aura/chrome_shell_delegate.h"
 #include "ui/aura/desktop.h"
 #include "ui/aura_shell/shell.h"
 
 #if defined(OS_CHROMEOS)
@@ skipping 12 matching lines @@
 
 void ChromeBrowserPartsAura::ToolkitInitialized() {
 }
 
 void ChromeBrowserPartsAura::PreMainMessageLoopStart() {
 }
 
 void ChromeBrowserPartsAura::PostMainMessageLoopStart() {
 }
 
-void ChromeBrowserPartsAura::PreMainMessageLoopRun() {
+content::IOThreadDelegate* ChromeBrowserPartsAura::PreMainMessageLoopRun() {
 #if defined(OS_CHROMEOS)
   if (chromeos::system::runtime_environment::IsRunningOnChromeOS())
     aura::Desktop::set_use_fullscreen_host_window(true);
 #endif
 
   // Shell takes ownership of ChromeShellDelegate.
   aura_shell::Shell::GetInstance()->SetDelegate(new ChromeShellDelegate);
+  return NULL;
 }
 
 bool ChromeBrowserPartsAura::MainMessageLoopRun(int* result_code) {
   return false;
 }
 
 void ChromeBrowserPartsAura::PostMainMessageLoopRun() {
 }