Add missing IWYU message_loop.h includes.

content/browser/appcache/appcache_url_request_job_unittest.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 "content/browser/appcache/appcache_url_request_job.h"
 
 #include <stdint.h>
 #include <string.h>
 
 #include <memory>
 #include <stack>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/message_loop/message_loop.h"
 #include "base/pickle.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "content/browser/appcache/appcache_response.h"
 #include "content/browser/appcache/mock_appcache_service.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
 #include "net/base/request_priority.h"
@@ skipping 863 matching lines @@
 
 TEST_F(AppCacheURLRequestJobTest, CancelRequest) {
   RunTestOnIOThread(&AppCacheURLRequestJobTest::CancelRequest);
 }
 
 TEST_F(AppCacheURLRequestJobTest, CancelRequestWithIOPending) {
   RunTestOnIOThread(&AppCacheURLRequestJobTest::CancelRequestWithIOPending);
 }
 
 }  // namespace content