Rename ash desktop_background to wallpaper.

ash/mus/container_ids.cc

 // Copyright 2016 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/mus/container_ids.h"
 
 #include "ash/common/shell_window_ids.h"
 #include "ash/public/interfaces/container.mojom.h"
 
 using ash::mojom::Container;
 
 namespace ash {
 namespace mus {
 
 int MashContainerToAshShellWindowId(Container container) {
   switch (container) {
-    case Container::USER_BACKGROUND:
-      return kShellWindowId_DesktopBackgroundContainer;
+    case Container::WALLPAPER:
+      return kShellWindowId_WallpaperContainer;
 
     case Container::USER_PRIVATE_SHELF:
       return kShellWindowId_ShelfContainer;
 
     case Container::LOGIN_WINDOWS:
       return kShellWindowId_LockScreenContainer;
 
     case Container::STATUS:
       return kShellWindowId_StatusContainer;
 
     case Container::BUBBLES:
       // TODO(sky): this mapping isn't right, but BUBBLES should go away once
       // http://crbug.com/616859 lands.
       return kShellWindowId_SettingBubbleContainer;
 
     case Container::MENUS:
       return kShellWindowId_MenuContainer;
 
     case Container::DRAG_AND_TOOLTIPS:
       return kShellWindowId_DragImageAndTooltipContainer;
 
     case Container::OVERLAY:
       return kShellWindowId_OverlayContainer;
   }
   return kShellWindowId_Invalid;
 }
 
 }  // namespace mus
 }  // namespace ash