Use a direct include of the message_loop header in chrome/test/, chrome/tools/, chrome/utility/.

chrome/test/base/test_tab_strip_model_observer.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/test/base/test_tab_strip_model_observer.h"
 
 #include "base/bind.h"
-#include "base/message_loop.h"
+#include "base/message_loop/message_loop.h"
 #include "chrome/browser/printing/print_preview_dialog_controller.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/render_view_host_observer.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/test/js_injection_ready_observer.h"
 
 class TestTabStripModelObserver::RenderViewHostInitializedObserver
@@ skipping 55 matching lines @@
   printing::PrintPreviewDialogController* dialog_controller =
       printing::PrintPreviewDialogController::GetInstance();
   if (!dialog_controller)
     return;
   content::WebContents* preview_dialog =
       dialog_controller->GetPrintPreviewForContents(contents);
   if (!preview_dialog)
     return;
   RegisterAsObserver(preview_dialog);
 }