Remove use of index in wallpaper picker code and some refactor

ash/shell_factory.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_FACTORY_H_
 #define ASH_SHELL_FACTORY_H_
 
 #include "ash/ash_export.h"
-#include "ash/desktop_background/desktop_background_resources.h"
 
 namespace aura {
 class RootWindow;
 }
 
 namespace gfx {
 class ImageSkia;
 }
 
 namespace ui_controls {
@@ skipping 15 matching lines @@
 
 ASH_EXPORT views::Widget* CreateStatusArea(views::View* contents);
 
 ui_controls::UIControlsAura* CreateUIControls();
 }  // namespace internal
 
 }  // namespace ash
 
 
 #endif  // ASH_SHELL_FACTORY_H_