Add missing IWYU message_loop.h includes.

chrome/test/chromedriver/commands_unittest.cc

 // Copyright (c) 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/test/chromedriver/commands.h"
 
 #include <stddef.h>
 
 #include <memory>
 #include <string>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/thread.h"
 #include "base/values.h"
 #include "chrome/test/chromedriver/chrome/status.h"
 #include "chrome/test/chromedriver/chrome/stub_chrome.h"
 #include "chrome/test/chromedriver/chrome/stub_web_view.h"
 #include "chrome/test/chromedriver/chrome/web_view.h"
 #include "chrome/test/chromedriver/command_listener_proxy.h"
@@ skipping 803 matching lines @@
       cmd,
       false,
       params,
       id,
       base::Bind(&OnFailBecauseErrorNotifyingListeners, &run_loop));
   run_loop.Run();
 
   thread->task_runner()->PostTask(FROM_HERE,
                                   base::Bind(&VerifySessionWasDeleted));
 }