Create a secondary file thread, FILE_USER_BLOCKING...

chrome/browser/metrics/thread_watcher.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/metrics/thread_watcher.h"
 
 #include <math.h>  // ceil
 
 #include "base/bind.h"
 #include "base/debug/alias.h"
@@ skipping 475 matching lines @@
                 live_threads_threshold);
   StartWatching(BrowserThread::DB, "DB", kSleepTime, kUnresponsiveTime,
                 unresponsive_threshold, crash_on_hang_thread_names,
                 live_threads_threshold);
   StartWatching(BrowserThread::FILE, "FILE", kSleepTime, kUnresponsiveTime,
                 unresponsive_threshold, crash_on_hang_thread_names,
                 live_threads_threshold);
   StartWatching(BrowserThread::CACHE, "CACHE", kSleepTime, kUnresponsiveTime,
                 unresponsive_threshold, crash_on_hang_thread_names,
                 live_threads_threshold);
+  StartWatching(BrowserThread::APPCACHE, "APPCACHE",
+                kSleepTime, kUnresponsiveTime,
+                unresponsive_threshold, crash_on_hang_thread_names,
+                live_threads_threshold);
 
   BrowserThread::PostTask(
       BrowserThread::UI,
       FROM_HERE,
       NewRunnableFunction(StartupTimeBomb::Disarm));
 }
 
 // static
 void ThreadWatcherList::StartWatching(
     const BrowserThread::ID& thread_id,
@@ skipping 279 matching lines @@
 
 #if defined(OS_WIN)
   // On Windows XP, give twice the time for shutdown.
   if (base::win::GetVersion() <= base::win::VERSION_XP)
     actual_duration *= 2;
 #endif
 
   shutdown_watchdog_ = new ShutdownWatchDogThread(actual_duration);
   shutdown_watchdog_->Arm();
 }