Add missing IWYU message_loop.h includes.

chrome/browser/profiles/profile_manager_browsertest.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 <stddef.h>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
+#include "base/message_loop/message_loop.h"
 #include "base/stl_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
 #include "chrome/browser/lifetime/keep_alive_types.h"
 #include "chrome/browser/lifetime/scoped_keep_alive.h"
 #include "chrome/browser/password_manager/password_store_factory.h"
 #include "chrome/browser/profiles/profile_attributes_entry.h"
 #include "chrome/browser/profiles/profile_attributes_storage.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/browser/profiles/profile_window.h"
@@ skipping 624 matching lines @@
 
   EXPECT_FALSE(profile->HasOffTheRecordProfile());
   EXPECT_FALSE(profile_manager->IsValidProfile(incognito_profile));
   EXPECT_EQ(initial_profile_count, profile_manager->GetNumberOfProfiles());
   // After destroying the incognito profile incognito preferences should be
   // cleared so the default save path should be taken from the main profile.
   EXPECT_FALSE(profile->GetOffTheRecordPrefs()
                    ->GetFilePath(prefs::kSaveFileDefaultDirectory)
                    .empty());
 }