Add missing IWYU message_loop.h includes.

chrome/browser/ui/search/instant_extended_interactive_uitest.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 <stdint.h>
 
 #include <sstream>
 
 #include "base/base_switches.h"
 #include "base/command_line.h"
 #include "base/macros.h"
+#include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram_base.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/run_loop.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "chrome/browser/bookmarks/bookmark_model_factory.h"
@@ skipping 713 matching lines @@
   stream << "link.href = \"" << result_url.spec() << "\";";
   stream << "document.body.appendChild(link);";
   stream << "link.click();";
   EXPECT_TRUE(content::ExecuteScript(contents, stream.str()));
 
   content::WaitForLoadStop(contents);
   std::string expected_title =
       "Referrer is " + instant_url().GetWithEmptyPath().spec();
   EXPECT_EQ(ASCIIToUTF16(expected_title), contents->GetTitle());
 }