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

chrome/browser/ui/app_modal_dialogs/app_modal_dialog_queue.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_APP_MODAL_DIALOGS_APP_MODAL_DIALOG_QUEUE_H_
 #define CHROME_BROWSER_UI_APP_MODAL_DIALOGS_APP_MODAL_DIALOG_QUEUE_H_
 #pragma once
 
 #include <queue>
 
-#include "base/singleton.h"
 #include "chrome/browser/ui/app_modal_dialogs/app_modal_dialog.h"
 
+template <typename T> struct DefaultSingletonTraits;
+
 // Keeps a queue of AppModalDialogs, making sure only one app modal
 // dialog is shown at a time.
 // This class is a singleton.
 class AppModalDialogQueue {
  public:
+  // Returns the singleton instance.
+  static AppModalDialogQueue* GetInstance();
+
   // Adds a modal dialog to the queue, if there are no other dialogs in the
   // queue, the dialog will be shown immediately. Once it is shown, the
   // most recently active browser window (or whichever is currently active)
   // will be app modal, meaning it will be activated if the user tries to
   // activate any other browser windows. So the dialog being shown should
   // assure it is the child of BrowserList::GetLastActive() so that it is
   // activated as well. See browser_list.h for more notes about our somewhat
   // sloppy app modality.
   // Note: The AppModalDialog |dialog| must be window modal before it
   // can be added as app modal.
@@ skipping 47 matching lines @@
   AppModalDialog* active_dialog_;
 
   // Stores if |ShowModalDialog()| is currently being called on an app-modal
   // dialog.
   bool showing_modal_dialog_;
 
   DISALLOW_COPY_AND_ASSIGN(AppModalDialogQueue);
 };
 
 #endif  // CHROME_BROWSER_UI_APP_MODAL_DIALOGS_APP_MODAL_DIALOG_QUEUE_H_