[gnome-software] trivial: Sync HighContrast CSS with the regular one

[Kalev Lember <klember src gnome org>]

commit c5790f71e88ab858a502ea611ce347e100d1a317
Author: Kalev Lember <klember redhat com>
Date:   Sun Sep 13 13:44:41 2015 +0200

    trivial: Sync HighContrast CSS with the regular one

 src/gtk-style-hc.css |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)
---
diff --git a/src/gtk-style-hc.css b/src/gtk-style-hc.css
index e737b2a..e222160 100644
--- a/src/gtk-style-hc.css
+++ b/src/gtk-style-hc.css
@@ -152,8 +152,14 @@ GtkBox.star {
        padding: 0px 4px;
 }
 
+/* the following two selectors are to color the small gap before the list inside the scrolled window
+   setting a background on the scrolled window affects the undershoot and the overshoot so explicitelly
+   excluding with :not() */
 .category-sidebar:not(.undershoot):not(.overshoot) { background-color: @theme_base_color; }
 
+.category-sidebar:backdrop:not(.undershoot):not(.overshoot) { background-color: @theme_unfocused_base_color; 
}
+
+/* Superfluous borders removal */
 .category-sidebar {
        border-style: none;
 }
@@ -166,7 +172,6 @@ GtkBox.star {
        border-right-style: solid;
 }
 
-
 .dimmer-label {
        opacity: 0.25;
        text-shadow: none;