Add missing IWYU message_loop.h includes.

ui/views/examples/examples_window.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 "ui/views/examples/examples_window.h"
 
 #include <algorithm>
 #include <iterator>
 #include <string>
 #include <utility>
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
+#include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/models/combobox_model.h"
 #include "ui/base/ui_base_paths.h"
 #include "ui/views/background.h"
 #include "ui/views/controls/combobox/combobox.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/examples/bubble_example.h"
 #include "ui/views/examples/button_example.h"
 #include "ui/views/examples/button_sticker_sheet.h"
@@ skipping 208 matching lines @@
     widget->Show();
   }
 }
 
 void LogStatus(const std::string& string) {
   ExamplesWindowContents::instance()->SetStatus(string);
 }
 
 }  // namespace examples
 }  // namespace views