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

ash/accelerators/accelerator_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/accelerators/accelerator_controller.h"
 
 #include "ash/caps_lock_delegate.h"
 #include "ash/ime_control_delegate.h"
 #include "ash/launcher/launcher.h"
 #include "ash/launcher/launcher_model.h"
@@ skipping 181 matching lines @@
       new ui::LayerAnimationSequence(new ui::ScreenRotation(delta)));
   screen_rotation->AddObserver(ash::Shell::GetRootWindow());
   ash::Shell::GetRootWindow()->layer()->GetAnimator()->StartAnimation(
       screen_rotation.release());
   return true;
 }
 
 bool HandleToggleDesktopBackgroundMode() {
   ash::Shell* shell = ash::Shell::GetInstance();
   if (shell->desktop_background_mode() == ash::Shell::BACKGROUND_IMAGE)
-    shell->SetDesktopBackgroundMode(ash::Shell::BACKGROUND_SOLID_COLOR);
-  else
-    shell->SetDesktopBackgroundMode(ash::Shell::BACKGROUND_IMAGE);
+    shell->SetDesktopBackgroundSolidColor();
+  else {
+    shell->SetDesktopBackgroundImage(ash::Shell::GetInstance()->
+                                     desktop_background_controller()->
+                                     GetUserWallpaper());
+  }
   return true;
 }
 
 bool HandleToggleRootWindowFullScreen() {
   ash::Shell::GetRootWindow()->ToggleFullScreen();
   return true;
 }
 
 bool HandlePrintLayerHierarchy() {
   aura::RootWindow* root_window = ash::Shell::GetRootWindow();
@@ skipping 180 matching lines @@
       NOTREACHED() << "Unhandled action " << it->second;
   }
   return false;
 }
 
 bool AcceleratorController::CanHandleAccelerators() const {
   return true;
 }
 
 }  // namespace ash