Remove "set wallpaper..." option in system context menu when guest logged in

ash/shell.h

 // Copyright (c) 2012 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 ASH_SHELL_H_
 #define ASH_SHELL_H_
 #pragma once
 
 #include <utility>
 #include <vector>
@@ skipping 54 matching lines @@
 class FocusCycler;
 class InputMethodEventFilter;
 class KeyRewriterEventFilter;
 class MonitorController;
 class PartialScreenshotEventFilter;
 class ResizeShadowController;
 class RootWindowEventFilter;
 class RootWindowLayoutManager;
 class ShadowController;
 class ShelfLayoutManager;
+class ShellContextMenu;
 class SystemGestureEventFilter;
 class StackingController;
 class TooltipController;
 class VisibilityController;
 class WindowModalityController;
 class WorkspaceController;
 }
 
 // Shell is a singleton object that presents the Shell API and implements the
 // RootWindow's delegate interface.
@@ skipping 199 matching lines @@
 #endif  // !defined(OS_MACOSX)
 
   scoped_ptr<ShellDelegate> delegate_;
   scoped_ptr<SystemTrayDelegate> tray_delegate_;
   scoped_ptr<UserWallpaperDelegate> user_wallpaper_delegate_;
 
   scoped_ptr<Launcher> launcher_;
 
   scoped_ptr<internal::AppList> app_list_;
 
+  scoped_ptr<internal::ShellContextMenu> shell_context_menu_;
   scoped_ptr<internal::StackingController> stacking_controller_;
   scoped_ptr<internal::ActivationController> activation_controller_;
   scoped_ptr<internal::WindowModalityController> window_modality_controller_;
   scoped_ptr<internal::DragDropController> drag_drop_controller_;
   scoped_ptr<internal::WorkspaceController> workspace_controller_;
   scoped_ptr<internal::ResizeShadowController> resize_shadow_controller_;
   scoped_ptr<internal::ShadowController> shadow_controller_;
   scoped_ptr<internal::TooltipController> tooltip_controller_;
   scoped_ptr<internal::VisibilityController> visibility_controller_;
   scoped_ptr<DesktopBackgroundController> desktop_background_controller_;
@@ skipping 38 matching lines @@
   // System tray with clock, Wi-Fi signal, etc. (a replacement in progress for
   // |status_widget_|).
   scoped_ptr<SystemTray> tray_;
 
   DISALLOW_COPY_AND_ASSIGN(Shell);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_H_