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

ash/desktop_background/desktop_background_view.h

Index: ash/desktop_background/desktop_background_view.h
diff --git a/ash/desktop_background/desktop_background_view.h b/ash/desktop_background/desktop_background_view.h
index 6af658325a6423f13ad9e61ed3b0852a91ba986c..4e11393b8e2ab81f744141c4053292231741bd30 100644
--- a/ash/desktop_background/desktop_background_view.h
+++ b/ash/desktop_background/desktop_background_view.h
@@ -15,9 +15,14 @@ namespace internal {
 
 class DesktopBackgroundView : public views::WidgetDelegateView {
  public:
-  DesktopBackgroundView();
+  DesktopBackgroundView(const SkBitmap& wallpaper);
   virtual ~DesktopBackgroundView();
 
+  // TODO(bshe): Remove this function once issue 117244 is fixed. It is
+  // currently used in DesktopBackgroundController::
+  // OnDesktopBackgroundChange.
+  void SetWallpaper(const SkBitmap& wallpaper);
+
  private:
   // Overridden from views::View:
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;