Add missing IWYU message_loop.h includes.

chrome/browser/service_process/service_process_control_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 "chrome/browser/service_process/service_process_control.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/location.h"
+#include "base/message_loop/message_loop.h"
 #include "base/path_service.h"
 #include "base/process/kill.h"
 #include "base/process/process.h"
 #include "base/process/process_iterator.h"
 #include "base/single_thread_task_runner.h"
 #include "base/test/test_timeouts.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "chrome/browser/ui/browser.h"
@@ skipping 347 matching lines @@
   // Callback should not be called during GetHistograms call.
   EXPECT_CALL(*this, MockHistogramsCallback()).Times(0);
   // Wait for real callback by providing large timeout value.
   EXPECT_TRUE(ServiceProcessControl::GetInstance()->GetHistograms(
       base::Bind(&ServiceProcessControlBrowserTest::HistogramsCallback,
                 base::Unretained(this)),
       base::TimeDelta::FromHours(1)));
   EXPECT_CALL(*this, MockHistogramsCallback()).Times(1);
   content::RunMessageLoop();
 }