Add missing IWYU message_loop.h includes.

services/service_manager/tests/lifecycle/app_client.cc

 // Copyright 2016 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/service_manager/tests/lifecycle/app_client.h"
 
 #include "base/macros.h"
+#include "base/message_loop/message_loop.h"
 #include "services/service_manager/public/cpp/service_context.h"
 
 namespace service_manager {
 namespace test {
 
 AppClient::AppClient() {
   registry_.AddInterface<mojom::LifecycleControl>(
       base::Bind(&AppClient::Create, base::Unretained(this)));
 }
 
@@ skipping 37 matching lines @@
       base::Bind(&AppClient::BindingLost, base::Unretained(this)));
 }
 
 void AppClient::BindingLost() {
   if (bindings_.empty())
     OnServiceManagerConnectionLost();
 }
 
 }  // namespace test
 }  // namespace service_manager