[gnome-shell] background: Adjust to gnome-desktop API break

[Florian Müllner <fmuellner src gnome org>]

commit f9a7718dda9641bf3750faba789edd701dfff5da
Author: Florian Müllner <fmuellner gnome org>
Date:   Sat Jul 20 12:11:55 2019 +0200

    background: Adjust to gnome-desktop API break
    
    gnome-desktop broke API in commit ca5d61cf24, as it didn't *add* a property
    as incorrectly stated in the commit message, but *replaced* an existing one.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/issues/1457

 js/ui/background.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/js/ui/background.js b/js/ui/background.js
index 0c0049b00..16bd1c573 100644
--- a/js/ui/background.js
+++ b/js/ui/background.js
@@ -633,7 +633,7 @@ var Animation = class Animation {
     }
 
     load(callback) {
-        this._show = new GnomeDesktop.BGSlideShow({ filename: this.file.get_path() });
+        this._show = new GnomeDesktop.BGSlideShow({ file: this.file });
 
         this._show.load_async(null, (object, result) => {
             this.loaded = true;