Add missing IWYU message_loop.h includes.

chrome/browser/sessions/session_restore.cc

 // Copyright 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 "chrome/browser/sessions/session_restore.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <list>
 #include <memory>
 #include <set>
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/debug/alias.h"
 #include "base/location.h"
 #include "base/macros.h"
+#include "base/message_loop/message_loop.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/lifetime/keep_alive_types.h"
@@ skipping 811 matching lines @@
 // static
 SessionRestore::CallbackSubscription
     SessionRestore::RegisterOnSessionRestoredCallback(
         const base::Callback<void(int)>& callback) {
   return on_session_restored_callbacks()->Add(callback);
 }
 
 // static
 base::CallbackList<void(int)>*
     SessionRestore::on_session_restored_callbacks_ = nullptr;