Remove message_loop_helpers.h and update the includes to point to the new location.

chrome/browser/printing/print_dialog_gtk.h

 // 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.
 
 #ifndef CHROME_BROWSER_PRINTING_PRINT_DIALOG_GTK_H_
 #define CHROME_BROWSER_PRINTING_PRINT_DIALOG_GTK_H_
 #pragma once
 
 #include <gtk/gtk.h>
 #include <gtk/gtkunixprint.h>
 
 #include "base/compiler_specific.h"
 #include "base/file_path.h"
 #include "base/memory/ref_counted.h"
-#include "base/message_loop_helpers.h"
+#include "base/sequenced_task_runner_helpers.h"
 #include "content/public/browser/browser_thread.h"
 #include "printing/print_dialog_gtk_interface.h"
 #include "printing/printing_context_gtk.h"
 #include "ui/base/gtk/gtk_signal.h"
 
 namespace printing {
 class Metafile;
 class PrintSettings;
 }
 
@@ skipping 58 matching lines @@
   GtkPrintSettings* gtk_settings_;
   GtkPageSetup* page_setup_;
   GtkPrinter* printer_;
 
   FilePath path_to_pdf_;
 
   DISALLOW_COPY_AND_ASSIGN(PrintDialogGtk);
 };
 
 #endif  // CHROME_BROWSER_PRINTING_PRINT_DIALOG_GTK_H_