Add a new GetInstance() method for singleton classes used in chrome/browser files.

chrome/browser/ui/app_modal_dialogs/message_box_handler.cc

 // Copyright (c) 2010 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/ui/app_modal_dialogs/message_box_handler.h"
 
 #include "app/l10n_util.h"
 #include "app/message_box_flags.h"
 #include "app/text_elider.h"
 #include "base/i18n/rtl.h"
@@ skipping 52 matching lines @@
 void RunJavascriptMessageBox(Profile* profile,
                              JavaScriptAppModalDialogDelegate* delegate,
                              const GURL& frame_url,
                              int dialog_flags,
                              const std::wstring& message_text,
                              const std::wstring& default_prompt_text,
                              bool display_suppress_checkbox,
                              IPC::Message* reply_msg) {
   bool is_alert = dialog_flags == MessageBoxFlags::kIsJavascriptAlert;
   std::wstring title = GetTitle(profile, is_alert, frame_url);
-  Singleton<AppModalDialogQueue>()->AddDialog(new JavaScriptAppModalDialog(
+  AppModalDialogQueue::GetInstance()->AddDialog(new JavaScriptAppModalDialog(
       delegate, title, dialog_flags, message_text, default_prompt_text,
       display_suppress_checkbox, false, reply_msg));
 }
 
 void RunBeforeUnloadDialog(TabContents* tab_contents,
                            const std::wstring& message_text,
                            IPC::Message* reply_msg) {
   std::wstring full_message =
       message_text + L"\n\n" +
       l10n_util::GetString(IDS_BEFOREUNLOAD_MESSAGEBOX_FOOTER);
-  Singleton<AppModalDialogQueue>()->AddDialog(new JavaScriptAppModalDialog(
+  AppModalDialogQueue::GetInstance()->AddDialog(new JavaScriptAppModalDialog(
       tab_contents, l10n_util::GetString(IDS_BEFOREUNLOAD_MESSAGEBOX_TITLE),
       MessageBoxFlags::kIsJavascriptConfirm, message_text, std::wstring(),
       false, true, reply_msg));
 }