Enable user change background image in settings page in Aura build.

ash/shell.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/shell.h"
 
 #include <algorithm>
 
 #include "ash/app_list/app_list.h"
 #include "ash/ash_switches.h"
+#include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/drag_drop/drag_drop_controller.h"
 #include "ash/focus_cycler.h"
 #include "ash/ime/input_method_event_filter.h"
 #include "ash/launcher/launcher.h"
 #include "ash/shell_delegate.h"
 #include "ash/shell_factory.h"
 #include "ash/shell_window_ids.h"
 #include "ash/system/audio/tray_volume.h"
 #include "ash/system/brightness/tray_brightness.h"
 #include "ash/system/settings/tray_settings.h"
@@ skipping 446 matching lines @@
 
   window_modality_controller_.reset(new internal::WindowModalityController);
   AddRootWindowEventFilter(window_modality_controller_.get());
 
   visibility_controller_.reset(new internal::VisibilityController);
 
   tooltip_controller_.reset(new internal::TooltipController);
   AddRootWindowEventFilter(tooltip_controller_.get());
 
   drag_drop_controller_.reset(new internal::DragDropController);
+  desktop_background_controller_.reset(new DesktopBackgroundController);
   power_button_controller_.reset(new PowerButtonController);
   video_detector_.reset(new VideoDetector);
   window_cycle_controller_.reset(new WindowCycleController);
 }
 
 Shell::WindowMode Shell::ComputeWindowMode(CommandLine* command_line) const {
   if (compact_window_mode_for_test_)
     return MODE_COMPACT;
 
   // Some devices don't perform well with overlapping windows.
@@ skipping 187 matching lines @@
 void Shell::ResetLayoutManager(int container_id) {
   GetContainer(container_id)->SetLayoutManager(NULL);
 }
 
 void Shell::DisableWorkspaceGridLayout() {
   if (workspace_controller_.get())
     workspace_controller_->workspace_manager()->set_grid_size(0);
 }
 
 }  // namespace ash