Create a secondary file thread, FILE_USER_BLOCKING...

content/browser/appcache/chrome_appcache_service.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 "content/browser/appcache/chrome_appcache_service.h"
 
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/notification_service.h"
@@ skipping 15 matching lines @@
     scoped_refptr<quota::SpecialStoragePolicy> special_storage_policy) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
   cache_path_ = cache_path;
   resource_context_ = resource_context;
   registrar_.Add(
       this, content::NOTIFICATION_PURGE_MEMORY,
       content::NotificationService::AllSources());
 
   // Init our base class.
-  Initialize(cache_path_,
-             BrowserThread::GetMessageLoopProxyForThread(BrowserThread::DB),
-             BrowserThread::GetMessageLoopProxyForThread(BrowserThread::CACHE));
+  Initialize(
+      cache_path_,
+      BrowserThread::GetMessageLoopProxyForThread(
+          BrowserThread::FILE_USER_BLOCKING),
+      BrowserThread::GetMessageLoopProxyForThread(BrowserThread::CACHE));
   set_appcache_policy(this);
   set_special_storage_policy(special_storage_policy);
 }
 
 ChromeAppCacheService::~ChromeAppCacheService() {
 }
 
 bool ChromeAppCacheService::CanLoadAppCache(const GURL& manifest_url,
                                             const GURL& first_party) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
@@ skipping 10 matching lines @@
 }
 
 void ChromeAppCacheService::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   DCHECK(type == content::NOTIFICATION_PURGE_MEMORY);
   PurgeMemory();
 }