Add missing IWYU message_loop.h includes.

chrome/browser/chromeos/login/ui/login_display_host_impl.cc

 // Copyright 2014 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/ui/login_display_host_impl.h"
 
 #include <utility>
 #include <vector>
 
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/shell.h"
 #include "ash/shell_port.h"
 #include "ash/system/tray/system_tray.h"
 #include "ash/wallpaper/wallpaper_delegate.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/message_loop/message_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_split.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/browser_shutdown.h"
 #include "chrome/browser/chrome_notification_types.h"
@@ skipping 1364 matching lines @@
   // Chrome locale. Otherwise it will be lost if Chrome restarts.
   // Don't need to schedule pref save because setting initial local
   // will enforce preference saving.
   prefs->SetString(prefs::kApplicationLocale, locale);
   StartupUtils::SetInitialLocale(locale);
 
   TriggerShowLoginWizardFinish(locale, std::move(data));
 }
 
 }  // namespace chromeos