Add missing IWYU message_loop.h includes.

services/ui/service.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 "services/ui/service.h"
 
 #include <set>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/weak_ptr.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/threading/platform_thread.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
 #include "components/discardable_memory/service/discardable_shared_memory_manager.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "services/catalog/public/cpp/resource_loader.h"
 #include "services/catalog/public/interfaces/constants.mojom.h"
 #include "services/service_manager/public/c/main.h"
 #include "services/service_manager/public/cpp/connector.h"
@@ skipping 398 matching lines @@
     mojom::WindowServerTestRequest request) {
   if (!test_config_)
     return;
   mojo::MakeStrongBinding(
       base::MakeUnique<ws::WindowServerTestImpl>(window_server_.get()),
       std::move(request));
 }
 
 
 }  // namespace ui