Add missing IWYU message_loop.h includes.

chrome/browser/extensions/crx_installer_browsertest.cc

 // Copyright (c) 2012 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/extensions/crx_installer.h"
 
 #include <stddef.h>
 
 #include <utility>
 
 #include "base/at_exit.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_restrictions.h"
 #include "build/build_config.h"
 #include "chrome/browser/download/download_crx_util.h"
 #include "chrome/browser/extensions/browser_action_test_util.h"
 #include "chrome/browser/extensions/extension_browsertest.h"
 #include "chrome/browser/extensions/extension_install_prompt.h"
 #include "chrome/browser/extensions/extension_install_prompt_show_params.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/extension_tab_util.h"
@@ skipping 690 matching lines @@
     EXPECT_TRUE(WaitForCrxInstallerDone());
     const Extension* extension = installer->extension();
     ASSERT_TRUE(extension);
     ASSERT_EQ(extension_id, extension->id());
     EXPECT_TRUE(ExtensionPrefs::Get(profile())->AllowFileAccess(extension_id));
     EXPECT_TRUE(extension->creation_flags() & Extension::ALLOW_FILE_ACCESS);
   }
 }
 
 }  // namespace extensions