Add missing IWYU message_loop.h includes.

chrome/browser/importer/profile_writer_unittest.cc

 // Copyright 2013 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/importer/profile_writer.h"
 
 #include <stddef.h>
 
 #include <string>
 
 #include "base/macros.h"
+#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/bookmarks/bookmark_model_factory.h"
 #include "chrome/browser/history/history_service_factory.h"
 #include "chrome/browser/importer/importer_unittest_utils.h"
 #include "chrome/common/importer/imported_bookmark_entry.h"
 #include "chrome/test/base/testing_profile.h"
 #include "components/bookmarks/browser/bookmark_model.h"
 #include "components/bookmarks/browser/bookmark_utils.h"
 #include "components/bookmarks/browser/titled_url_match.h"
@@ skipping 179 matching lines @@
       new TestProfileWriter(&profile));
   profile_writer->AddHistoryPage(pages_, history::SOURCE_FIREFOX_IMPORTED);
   VerifyHistoryCount(&profile);
   size_t original_history_count = history_count_;
   history_count_ = 0;
 
   profile_writer->AddHistoryPage(pages_, history::SOURCE_FIREFOX_IMPORTED);
   VerifyHistoryCount(&profile);
   EXPECT_EQ(original_history_count, history_count_);
 }