[gnome-shell] magnifier: Adapt to painting and picking API change

[Florian Müllner <fmuellner src gnome org>]

commit 0795d8df5f6ad3f7e2d67403e14b805e14c87e6d
Author: Robert Mader <robert mader posteo de>
Date:   Fri Dec 6 20:10:58 2019 +0100

    magnifier: Adapt to painting and picking API change
    
    This was left out in 988a0e7314018
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/891

 js/ui/magnifier.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/js/ui/magnifier.js b/js/ui/magnifier.js
index a5e6c22d77..fe1ca3e091 100644
--- a/js/ui/magnifier.js
+++ b/js/ui/magnifier.js
@@ -55,7 +55,7 @@ var MouseSpriteContent = GObject.registerClass({
         return [true, this._texture.get_width(), this._texture.get_height()];
     }
 
-    vfunc_paint_content(actor, node) {
+    vfunc_paint_content(actor, node, _paintContext) {
         if (!this._texture)
             return;