mash: Port mojo:ash_sysui's ContextMenuMus to mojo:ash.

ash/desktop_background/desktop_background_controller.cc

 // 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.
 
 #include "ash/desktop_background/desktop_background_controller.h"
 
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/display/display_info.h"
 #include "ash/common/shell_window_ids.h"
+#include "ash/common/wallpaper/wallpaper_delegate.h"
 #include "ash/common/wm_shell.h"
 #include "ash/desktop_background/desktop_background_controller_observer.h"
 #include "ash/desktop_background/desktop_background_view.h"
 #include "ash/desktop_background/desktop_background_widget_controller.h"
-#include "ash/desktop_background/user_wallpaper_delegate.h"
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "components/wallpaper/wallpaper_resizer.h"
 #include "ui/aura/window.h"
 #include "ui/display/screen.h"
 #include "ui/views/widget/widget.h"
 
@@ skipping 220 matching lines @@
   return moved;
 }
 
 int DesktopBackgroundController::GetBackgroundContainerId(bool locked) {
   return locked ? kShellWindowId_LockScreenBackgroundContainer
                 : kShellWindowId_DesktopBackgroundContainer;
 }
 
 void DesktopBackgroundController::UpdateWallpaper(bool clear_cache) {
   current_wallpaper_.reset();
-  Shell::GetInstance()->user_wallpaper_delegate()->UpdateWallpaper(clear_cache);
+  WmShell::Get()->wallpaper_delegate()->UpdateWallpaper(clear_cache);
 }
 
 }  // namespace ash