Move ProxyConfigService construction onto the IO thread.

content/shell/shell_resource_context.cc

 // Copyright (c) 2012 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 "content/shell/shell_resource_context.h"
 #include "content/shell/shell_url_request_context_getter.h"
 
 namespace content {
 
 ShellResourceContext::ShellResourceContext(
     ShellURLRequestContextGetter* getter)
     : getter_(getter) {
 }
 
 ShellResourceContext::~ShellResourceContext() {
 }
 
+void ShellResourceContext::StartTearDown() {
+  getter_->StartTearDown();
+}
+
 net::HostResolver* ShellResourceContext::GetHostResolver() {
   return getter_->host_resolver();
 }
 
 net::URLRequestContext* ShellResourceContext::GetRequestContext() {
   return getter_->GetURLRequestContext();
 }
 
 }  // namespace content