[gnome-shell] background: Use actor.content.background

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 75235624b2d7d84c4173846e526a1e9beaaccb8d
Author: Daniel van Vugt <daniel van vugt canonical com>
Date:   Wed Jul 1 18:51:33 2020 +0800

    background: Use actor.content.background
    
    Because actor.background no longer exists and emitted errors when
    referenced.
    
    Closes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2949
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1343

 js/ui/background.js | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/js/ui/background.js b/js/ui/background.js
index b7bf2b1a08..20f5e89126 100644
--- a/js/ui/background.js
+++ b/js/ui/background.js
@@ -712,13 +712,18 @@ var BackgroundManager = class BackgroundManager {
         }
 
         let newBackgroundActor = this._createBackgroundActor();
-        newBackgroundActor.vignette_sharpness = this.backgroundActor.vignette_sharpness;
-        newBackgroundActor.brightness = this.backgroundActor.brightness;
+
+        const oldContent = this.backgroundActor.content;
+        const newContent = newBackgroundActor.content;
+
+        newContent.vignette_sharpness = oldContent.vignette_sharpness;
+        newContent.brightness = oldContent.brightness;
+
         newBackgroundActor.visible = this.backgroundActor.visible;
 
         this._newBackgroundActor = newBackgroundActor;
 
-        let background = newBackgroundActor.background;
+        const { background } = newBackgroundActor.content;
 
         if (background.isLoaded) {
             this._swapBackgroundActor();