GTK: Buttons on Confirm Infobars should have matching sizes.

chrome/browser/ui/gtk/infobars/confirm_infobar_gtk.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_GTK_INFOBARS_CONFIRM_INFOBAR_GTK_H_
 #define CHROME_BROWSER_UI_GTK_INFOBARS_CONFIRM_INFOBAR_GTK_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "chrome/browser/tab_contents/confirm_infobar_delegate.h"
 #include "chrome/browser/ui/gtk/infobars/infobar_gtk.h"
 #include "ui/base/gtk/gtk_signal.h"
 
+typedef struct _GtkSizeGroup GtkSizeGroup;
 typedef struct _GtkWidget GtkWidget;
 
 // An infobar that shows a message, up to two optional buttons, and an optional,
 // right-aligned link. This is commonly used to do things like:
 // "Would you like to do X? [Yes] [No]                         _Learn More_ [x]"
 class ConfirmInfoBarGtk : public InfoBar {
  public:
   explicit ConfirmInfoBarGtk(ConfirmInfoBarDelegate* delegate);
 
  private:
   virtual ~ConfirmInfoBarGtk();
 
   // Adds a button to the info bar by type. It will do nothing if the delegate
   // doesn't specify a button of the given type.
   void AddButton(ConfirmInfoBarDelegate::InfoBarButton type);
 
   CHROMEGTK_CALLBACK_0(ConfirmInfoBarGtk, void, OnOkButton);
   CHROMEGTK_CALLBACK_0(ConfirmInfoBarGtk, void, OnCancelButton);
   CHROMEGTK_CALLBACK_0(ConfirmInfoBarGtk, void, OnLinkClicked);
 
   GtkWidget* confirm_hbox_;
 
+  GtkSizeGroup* size_group_;
+
   DISALLOW_COPY_AND_ASSIGN(ConfirmInfoBarGtk);
 };
 
 #endif  // CHROME_BROWSER_UI_GTK_INFOBARS_CONFIRM_INFOBAR_GTK_H_