Add missing IWYU message_loop.h includes.

ui/views/widget/widget_interactive_uitest.cc

 // Copyright (c) 2013 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 <stddef.h>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/location.h"
 #include "base/macros.h"
+#include "base/message_loop/message_loop.h"
 #include "base/path_service.h"
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/ime/text_input_client.h"
 #include "ui/base/resource/resource_bundle.h"
@@ skipping 1786 matching lines @@
 
   ui::KeyEvent key_event2(key_event);
   widget->OnKeyEvent(&key_event2);
   EXPECT_FALSE(key_event2.stopped_propagation());
 
   widget->CloseNow();
 }
 
 }  // namespace test
 }  // namespace views