gtk: Use gtk_dialog_get_content_area() throughout.

remoting/host/disconnect_window_linux.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.
 
 #include "remoting/host/disconnect_window.h"
 
 #include <gtk/gtk.h>
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
@@ skipping 46 matching lines @@
   // Try to keep the window always visible.
   gtk_window_stick(window);
   gtk_window_set_keep_above(window, TRUE);
   // Utility windows have no minimize button or taskbar presence.
   gtk_window_set_type_hint(window, GDK_WINDOW_TYPE_HINT_UTILITY);
   gtk_window_set_deletable(window, FALSE);
 
   g_signal_connect(disconnect_window_, "response",
                    G_CALLBACK(OnResponseThunk), this);
 
-  GtkWidget* content_area = GTK_DIALOG(disconnect_window_)->vbox;
+  GtkWidget* content_area =
+      gtk_dialog_get_content_area(GTK_DIALOG(disconnect_window_));
 
   GtkWidget* username_row = gtk_hbox_new(FALSE, 0);
   // TODO(lambroslambrou): Replace the magic number with an appropriate
   // constant from a header file (such as chrome/browser/ui/gtk/gtk_util.h
   // but check_deps disallows its #inclusion here).
   gtk_container_set_border_width(GTK_CONTAINER(username_row), 12);
   gtk_container_add(GTK_CONTAINER(content_area), username_row);
 
   GtkWidget* share_label = gtk_label_new(kSharingWith);
   gtk_container_add(GTK_CONTAINER(username_row), share_label);
@@ skipping 27 matching lines @@
 
   host_->Shutdown(NULL);
   Hide();
 }
 
 DisconnectWindow* DisconnectWindow::Create() {
   return new DisconnectWindowLinux;
 }
 
 }  // namespace remoting