Add missing IWYU message_loop.h includes.

chrome/common/service_process_util_mac_unittest.mm

 // 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 "chrome/common/service_process_util.h"
 
 #import <Foundation/Foundation.h>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_nsobject.h"
+#include "base/message_loop/message_loop.h"
 #include "base/process/launch.h"
 #include "base/run_loop.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/test/test_timeouts.h"
 #include "base/threading/thread.h"
 #include "chrome/common/mac/launchd.h"
 #include "chrome/common/mac/mock_launchd.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 // Once Chrome no longer supports OSX 10.7, everything within this
@@ skipping 160 matching lines @@
 }
 
 TEST_F(ServiceProcessStateFileManipulationTest, ChangeAttr) {
   ScopedAttributesRestorer restorer(bundle_path(), 0777);
   GetIOTaskRunner()->PostTask(FROM_HERE,
                               base::Bind(&ChangeAttr, bundle_path(), 0222));
   Run();
   ASSERT_TRUE(mock_launchd()->remove_called());
   ASSERT_TRUE(mock_launchd()->delete_called());
 }