Add missing IWYU message_loop.h includes.

components/invalidation/impl/non_blocking_invalidator_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 "components/invalidation/impl/non_blocking_invalidator.h"
 
 #include <memory>
 
 #include "base/bind_helpers.h"
 #include "base/location.h"
 #include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/threading/thread.h"
 #include "components/invalidation/impl/fake_invalidation_handler.h"
 #include "components/invalidation/impl/invalidation_state_tracker.h"
 #include "components/invalidation/impl/invalidator_test_template.h"
 #include "google/cacheinvalidation/types.pb.h"
 #include "jingle/notifier/base/fake_base_task.h"
 #include "net/url_request/url_request_test_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 65 matching lines @@
   base::Thread io_thread_;
   scoped_refptr<net::URLRequestContextGetter> request_context_getter_;
   std::unique_ptr<NonBlockingInvalidator> invalidator_;
 };
 
 INSTANTIATE_TYPED_TEST_CASE_P(
     NonBlockingInvalidatorTest, InvalidatorTest,
     NonBlockingInvalidatorTestDelegate);
 
 }  // namespace syncer