Add missing IWYU message_loop.h includes.

chrome/chrome_watcher/chrome_watcher_main.cc

 // Copyright (c) 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 <windows.h>
 #include <sddl.h>
 
 #include <utility>
 
 #include "base/at_exit.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
 #include "base/environment.h"
 #include "base/file_version_info.h"
 #include "base/files/file_path.h"
 #include "base/logging_win.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop.h"
 #include "base/process/memory.h"
 #include "base/process/process.h"
 #include "base/run_loop.h"
 #include "base/sequenced_task_runner.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/waitable_event.h"
@@ skipping 197 matching lines @@
 
   // Wind logging down.
   logging::LogEventProvider::Uninitialize();
 
   return 0;
 }
 
 static_assert(
     std::is_same<decltype(&WatcherMain), ChromeWatcherMainFunction>::value,
     "WatcherMain() has wrong type");