[gnome-shell] overview: Don't show black panel on startup

[Marge Bot <marge-bot src gnome org>]

commit 9bce2a02beb4efbb0676f8e09d7b027c3bf72f4c
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Tue Mar 2 19:52:26 2021 -0300

    overview: Don't show black panel on startup
    
    The back → transparent transition gives it a very bad look when
    booting and running the startup animation.
    
    Use the same transition duration hack to ensure that the panel
    starts completely transparent.
    
    Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1678>

 js/ui/overview.js | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/js/ui/overview.js b/js/ui/overview.js
index 209be42030..78736e513e 100644
--- a/js/ui/overview.js
+++ b/js/ui/overview.js
@@ -652,6 +652,8 @@ var Overview = class {
     }
 
     runStartupAnimation(callback) {
+        Main.panel.style = 'transition-duration: 0ms;';
+
         this._shown = true;
         this._visible = true;
         this._visibleTarget = true;
@@ -663,6 +665,7 @@ var Overview = class {
         this.emit('showing');
 
         this._overview.runStartupAnimation(() => {
+            Main.panel.style = null;
             this.emit('shown');
             callback();
         });