Add a lock screen example.

ui/aura_shell/examples/example_factory.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 UI_AURA_SHELL_SHELL_FACTORY_H_
 #define UI_AURA_SHELL_SHELL_FACTORY_H_
 #pragma once
 
 #include "ui/gfx/native_widget_types.h"
 
 namespace gfx {
 class Point;
 }
 
 namespace aura_shell {
 namespace examples {
 
 void CreatePointyBubble(gfx::NativeWindow parent, const gfx::Point& origin);
 
+void CreateLock();
+
 }  // namespace examples
 }  // namespace aura_shell
 
 
 #endif  // UI_AURA_SHELL_SHELL_FACTORY_H_