Add missing IWYU message_loop.h includes.

components/suggestions/suggestions_service_impl_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/suggestions/suggestions_service_impl.h"
 
 #include <stdint.h>
 
 #include <memory>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/test/mock_callback.h"
 #include "base/test/scoped_feature_list.h"
 #include "components/signin/core/browser/account_tracker_service.h"
 #include "components/signin/core/browser/fake_profile_oauth2_token_service.h"
 #include "components/signin/core/browser/fake_signin_manager.h"
 #include "components/signin/core/browser/test_signin_client.h"
 #include "components/suggestions/blacklist_store.h"
 #include "components/suggestions/features.h"
 #include "components/suggestions/image_manager.h"
@@ skipping 714 matching lines @@
   EXPECT_CALL(*thumbnail_manager(), GetImageForURL(test_url, _));
   suggestions_service()->GetPageThumbnail(test_url, dummy_callback);
 
   EXPECT_CALL(*thumbnail_manager(), AddImageURL(test_url, thumbnail_url));
   EXPECT_CALL(*thumbnail_manager(), GetImageForURL(test_url, _));
   suggestions_service()->GetPageThumbnailWithURL(test_url, thumbnail_url,
                                                  dummy_callback);
 }
 
 }  // namespace suggestions