Add missing IWYU message_loop.h includes.

chrome/browser/ui/views/frame/browser_window_property_manager_browsertest_win.cc

 // Copyright 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 <objbase.h>
 #include <shlobj.h>  // Must be before propkey.
 #include <propkey.h>
 #include <shellapi.h>
 #include <stddef.h>
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/macros.h"
+#include "base/message_loop/message_loop.h"
 #include "base/strings/string16.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/scoped_comptr.h"
 #include "base/win/scoped_propvariant.h"
 #include "base/win/windows_version.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/extension_browsertest.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_attributes_entry.h"
 #include "chrome/browser/profiles/profile_attributes_storage.h"
@@ skipping 226 matching lines @@
   for (auto* b : *BrowserList::GetInstance()) {
     if (b != browser())
       app_browser = b;
   }
   ASSERT_TRUE(app_browser);
   ASSERT_TRUE(app_browser != browser());
 
   WaitAndValidateBrowserWindowProperties(
       base::Bind(&ValidateHostedAppWindowProperties, app_browser, extension));
 }