Temporary whitelist several cases of disk I/O on the UI threads in cros.

chrome/browser/chromeos/login/update_screen.cc

 // Copyright (c) 2010 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/chromeos/login/update_screen.h"
 
 #include "base/file_util.h"
 #include "base/logging.h"
+#include "base/threading/thread_restrictions.h"
 #include "chrome/browser/chromeos/cros/cros_library.h"
 #include "chrome/browser/chromeos/login/screen_observer.h"
 #include "chrome/browser/chromeos/login/update_view.h"
 #include "chrome/browser/chromeos/login/wizard_controller.h"
 
 namespace {
 
 // Progress bar stages. Each represents progress bar value
 // at the beginning of each stage.
 // TODO(nkostylev): Base stage progress values on approximate time.
@@ skipping 182 matching lines @@
     reboot_timer_.Stop();
   DCHECK(!reboot_timer_.IsRunning());
   reboot_check_delay_ = seconds;
 }
 
 bool UpdateScreen::HasCriticalUpdate() {
   if (is_all_updates_critical_)
     return true;
 
   std::string deadline;
+  // Checking for update flag file causes us to do blocking IO on UI thread.
+  // Temporarily allow it until we fix http://crosbug.com/11106
+  base::ThreadRestrictions::ScopedAllowIO allow_io;
   FilePath update_deadline_file_path(kUpdateDeadlineFile);
   if (!file_util::ReadFileToString(update_deadline_file_path, &deadline) ||
       deadline.empty()) {
     return false;
   }
 
   // TODO(dpolukhin): Analyze file content. Now we can just assume that
   // if the file exists and not empty, there is critical update.
   return true;
 }
 
 void UpdateScreen::SetAllUpdatesCritical(bool is_critical) {
   is_all_updates_critical_ = is_critical;
 }
 
 }  // namespace chromeos