Add missing IWYU message_loop.h includes.

ui/views/controls/menu/menu_controller_unittest.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 "ui/views/controls/menu/menu_controller.h"
 
 #include "base/callback.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/utf_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "ui/aura/scoped_window_targeter.h"
 #include "ui/aura/window.h"
 #include "ui/events/event.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/event_handler.h"
 #include "ui/events/event_utils.h"
@@ skipping 1393 matching lines @@
   // crash.
   TestAsyncEscapeKey();
   EXPECT_EQ(nested_controller_delegate_2->on_menu_closed_called(), 1);
   EXPECT_EQ(menu_controller_delegate(), GetCurrentDelegate());
 }
 
 #endif  // defined(USE_AURA)
 
 }  // namespace test
 }  // namespace views