Rename ash desktop_background to wallpaper.

ash/wm/root_window_layout_manager_unittest.cc

 // Copyright 2015 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/common/shell_window_ids.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
 #include "ui/aura/test/test_windows.h"
 #include "ui/aura/window_observer.h"
 
@@ skipping 16 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(WindowDeleter);
 };
 
 }  // namespace
 
 using RootWindowLayoutManagerTest = test::AshTestBase;
 
 TEST_F(RootWindowLayoutManagerTest, DeleteChildDuringResize) {
   aura::Window* parent = Shell::GetPrimaryRootWindow()->GetChildById(
-      kShellWindowId_DesktopBackgroundContainer);
+      kShellWindowId_WallpaperContainer);
   aura::Window* w1 = aura::test::CreateTestWindowWithId(1, parent);
   aura::Window* w2 = aura::test::CreateTestWindowWithId(2, parent);
   WindowDeleter deleter(w1);
   w2->AddObserver(&deleter);
   UpdateDisplay("600x500");
   w2->RemoveObserver(&deleter);
 }
 
 }  // namespace ash