Add missing IWYU message_loop.h includes.

chrome/browser/extensions/extension_service_unittest.cc

 // Copyright (c) 2013 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/extensions/extension_service.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 10 matching lines @@
 #include "base/files/file_enumerator.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/json/json_file_value_serializer.h"
 #include "base/json/json_reader.h"
 #include "base/json/json_string_value_serializer.h"
 #include "base/location.h"
 #include "base/macros.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/single_thread_task_runner.h"
 #include "base/stl_util.h"
 #include "base/strings/pattern.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/values.h"
@@ skipping 6917 matching lines @@
             shared_module->manifest()->type());
   EXPECT_TRUE(registry()->enabled_extensions().Contains(kExtensionId));
 
   // Reload the extension and wait for it to complete. This previously crashed
   // (see crbug.com/676815).
   service()->ReloadExtension(kExtensionId);
   base::RunLoop().RunUntilIdle();
   // The shared module should be enabled.
   EXPECT_TRUE(registry()->enabled_extensions().Contains(kExtensionId));
 }