Make BubbleWindow a Widget override with a BubbleFrameView.

chrome/browser/ui/views/extensions/extension_dialog.h

 // Copyright (c) 2011 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_VIEWS_EXTENSIONS_EXTENSION_DIALOG_H_
 #define CHROME_BROWSER_UI_VIEWS_EXTENSIONS_EXTENSION_DIALOG_H_
 #pragma once
 
 #include "base/memory/ref_counted.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "ui/views/widget/widget_delegate.h"
 
 class Browser;
 class ExtensionDialogObserver;
 class ExtensionHost;
 class GURL;
 class TabContents;
 
-namespace views {
-class View;
-class Widget;
-}
-
 // Modal dialog containing contents provided by an extension.
 // Dialog is automatically centered in the browser window and has fixed size.
 // For example, used by the Chrome OS file browser.
 class ExtensionDialog : public views::WidgetDelegate,
                         public content::NotificationObserver,
                         public base::RefCounted<ExtensionDialog> {
  public:
   virtual ~ExtensionDialog();
 
   // Create and show a dialog with |url| centered over the browser window.
@@ skipping 55 matching lines @@
 
   content::NotificationRegistrar registrar_;
 
   // The observer of this popup.
   ExtensionDialogObserver* observer_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionDialog);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_EXTENSIONS_EXTENSION_DIALOG_H_