Add missing IWYU message_loop.h includes.

components/certificate_reporting/error_report_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 "components/certificate_reporting/error_report.h"
 
 #include <set>
 #include <string>
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/memory/ptr_util.h"
+#include "base/message_loop/message_loop.h"
 #include "base/path_service.h"
 #include "base/threading/thread.h"
 #include "base/time/default_clock.h"
 #include "base/time/default_tick_clock.h"
 #include "components/certificate_reporting/cert_logger.pb.h"
 #include "components/network_time/network_time_test_utils.h"
 #include "components/prefs/testing_pref_service.h"
 #include "net/cert/cert_status_flags.h"
 #include "net/ssl/ssl_info.h"
 #include "net/test/cert_test_util.h"
@@ skipping 229 matching lines @@
   CertLoggerRequest parsed;
   ASSERT_TRUE(parsed.ParseFromString(serialized_report));
   EXPECT_EQ(CertLoggerFeaturesInfo::ANDROID_AIA_FETCHING_ENABLED,
             parsed.features_info().android_aia_fetching_status());
 }
 #endif
 
 }  // namespace
 
 }  // namespace certificate_reporting