[gnome-control-center/wip/exalm/headerbars] background: Adjust preview header bar style

[Alexander Mikhaylenko <alexm src gnome org>]

commit 38442303e06812bdec7a5ebbe0caa04590536bb3
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Tue Jun 28 22:36:06 2022 +0400

    background: Adjust preview header bar style
    
    There has been a slight change, sync to it.

 panels/background/preview.css | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)
---
diff --git a/panels/background/preview.css b/panels/background/preview.css
index 654231932..e9497348b 100644
--- a/panels/background/preview.css
+++ b/panels/background/preview.css
@@ -12,7 +12,6 @@ background-preview .window {
 
 background-preview .window .header-bar {
   min-height: 15px;
-  box-shadow: inset 0 -1px @borders;
 }
 
 background-preview .window.light {
@@ -20,6 +19,10 @@ background-preview .window.light {
   color: alpha(black, .8);
 }
 
+background-preview .window.light .header-bar {
+  box-shadow: inset 0 -1px alpha(black, .07);
+}
+
 background-preview .window.front.light .header-bar {
   background-color: #ebebeb;
 }
@@ -29,6 +32,10 @@ background-preview .window.dark {
   color: white;
 }
 
+background-preview .window.dark .header-bar {
+  box-shadow: inset 0 -1px alpha(black, .36);
+}
+
 background-preview .window.front.dark .header-bar {
   background-color: #303030;
 }