gtk: Use gtk_dialog_get_content_area() throughout.

chrome/browser/ui/gtk/extensions/extension_uninstall_dialog_gtk.cc

 // 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.
 //
 // Currently this file is only used for the uninstall prompt. The install prompt
 // code is in extension_install_prompt2_gtk.cc.
 
 #include <gtk/gtk.h>
 
 #include "base/string_util.h"
@@ skipping 35 matching lines @@
       parent,
       GTK_DIALOG_MODAL,
       GTK_STOCK_CANCEL,
       GTK_RESPONSE_CLOSE,
       l10n_util::GetStringUTF8(IDS_EXTENSION_PROMPT_UNINSTALL_BUTTON).c_str(),
       GTK_RESPONSE_ACCEPT,
       NULL);
   gtk_dialog_set_has_separator(GTK_DIALOG(dialog), FALSE);
 
   // Create a two column layout.
-  GtkWidget* content_area = GTK_DIALOG(dialog)->vbox;
+  GtkWidget* content_area = gtk_dialog_get_content_area(GTK_DIALOG(dialog));
   gtk_box_set_spacing(GTK_BOX(content_area), gtk_util::kContentAreaSpacing);
 
   GtkWidget* icon_hbox = gtk_hbox_new(FALSE, gtk_util::kContentAreaSpacing);
   gtk_box_pack_start(GTK_BOX(content_area), icon_hbox, TRUE, TRUE, 0);
 
   // Put Icon in the left column.
   GdkPixbuf* pixbuf = gfx::GdkPixbufFromSkBitmap(skia_icon);
   GtkWidget* icon = gtk_image_new_from_pixbuf(pixbuf);
   g_object_unref(pixbuf);
   gtk_box_pack_start(GTK_BOX(icon_hbox), icon, TRUE, TRUE, 0);
@@ skipping 29 matching lines @@
 
   BrowserWindowGtk* browser_window = static_cast<BrowserWindowGtk*>(
       browser->window());
   if (!browser_window) {
     delegate->ExtensionDialogCanceled();
     return;
   }
 
   ShowUninstallDialogGtk(browser_window->window(), icon, extension, delegate);
 }