Add missing IWYU message_loop.h includes.

chrome/browser/ui/views/apps/app_info_dialog/app_info_dialog_views_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 "chrome/browser/ui/views/apps/app_info_dialog/app_info_dialog_views.h"
 
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/test_extension_environment.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/views/apps/app_info_dialog/app_info_header_panel.h"
 #include "chrome/common/extensions/extension_constants.h"
 #include "chrome/test/base/browser_with_test_window_test.h"
 #include "chrome/test/base/testing_profile.h"
 #include "extensions/browser/extension_system.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 279 matching lines @@
   extensions::ExtensionSystem::Get(other_profile.get())
       ->extension_service()
       ->AddExtension(other_app.get());
   ShowAppInfoForProfile(extension_misc::kChromeAppId, other_profile.get());
   EXPECT_FALSE(widget_->IsClosed());
   // The ARC App info links are not available if ARC is not allowed for
   // secondary profile.
   EXPECT_FALSE(dialog_->arc_app_info_links_for_test());
 }
 #endif