Add missing IWYU message_loop.h includes.

chrome/browser/safe_browsing/incident_reporting/state_store_unittest.cc

 // Copyright 2015 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/safe_browsing/incident_reporting/state_store.h"
 
 #include <stdint.h>
 
 #include "base/files/scoped_temp_dir.h"
 #include "base/json/json_file_value_serializer.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/test/test_simple_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/values.h"
 #include "build/build_config.h"
 #include "chrome/browser/prefs/browser_prefs.h"
 #include "chrome/browser/safe_browsing/incident_reporting/incident.h"
 #include "chrome/browser/safe_browsing/incident_reporting/platform_state_store.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/test/base/testing_browser_process.h"
@@ skipping 252 matching lines @@
     // Verify that the state survived.
     ASSERT_TRUE(state_store.HasBeenReported(data.type, data.key, data.digest));
 #else
     // Verify that the state did not survive.
     ASSERT_FALSE(state_store.HasBeenReported(data.type, data.key, data.digest));
 #endif
   }
 }
 
 }  // namespace safe_browsing