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

ash/desktop_background/desktop_background_view.cc

Index: ash/desktop_background/desktop_background_view.cc
diff --git a/ash/desktop_background/desktop_background_view.cc b/ash/desktop_background/desktop_background_view.cc
index dbf256f0499df461eccbaff9cee46a3b78ca9305..96c4a6ee6808cde8c8b2ff5a39d3ff2882ea199e 100644
--- a/ash/desktop_background/desktop_background_view.cc
+++ b/ash/desktop_background/desktop_background_view.cc
@@ -28,15 +28,20 @@ static int RoundPositive(double x) {
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopBackgroundView, public:
 
-DesktopBackgroundView::DesktopBackgroundView() {
-  wallpaper_ = *ui::ResourceBundle::GetSharedInstance().GetImageNamed(
-      IDR_AURA_WALLPAPER_1).ToSkBitmap();
+DesktopBackgroundView::DesktopBackgroundView(const SkBitmap& wallpaper) {
+  wallpaper_ = wallpaper;
   wallpaper_.buildMipMap(false);
 }
 
 DesktopBackgroundView::~DesktopBackgroundView() {
 }
 
+void DesktopBackgroundView::SetWallpaper(const SkBitmap& wallpaper) {
+  wallpaper_ = wallpaper;
+  wallpaper_.buildMipMap(false);
+  SchedulePaint();
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopBackgroundView, views::View overrides:
 
@@ -88,11 +93,11 @@ void DesktopBackgroundView::OnMouseReleased(const views::MouseEvent& event) {
     Shell::GetInstance()->ShowBackgroundMenu(GetWidget(), event.location());
 }
 
-views::Widget* CreateDesktopBackground() {
+views::Widget* CreateDesktopBackground(const SkBitmap& wallpaper) {
   views::Widget* desktop_widget = new views::Widget;
   views::Widget::InitParams params(
       views::Widget::InitParams::TYPE_WINDOW_FRAMELESS);
-  DesktopBackgroundView* view = new DesktopBackgroundView;
+  DesktopBackgroundView* view = new DesktopBackgroundView(wallpaper);
   params.delegate = view;
   params.parent =
       Shell::GetInstance()->GetContainer(