[gtk+] Adwaita: delete unused mixin

[Lapo Calamandrei <lapo src gnome org>]

commit 2184c910ebc0f3ac1d176250b2fb857323116b09
Author: Lapo Calamandrei <calamandrei gmail com>
Date:   Sat Apr 16 13:21:39 2016 +0200

    Adwaita: delete unused mixin

 gtk/theme/Adwaita/_drawing.scss |   26 --------------------------
 1 files changed, 0 insertions(+), 26 deletions(-)
---
diff --git a/gtk/theme/Adwaita/_drawing.scss b/gtk/theme/Adwaita/_drawing.scss
index 206387e..49bdd43 100644
--- a/gtk/theme/Adwaita/_drawing.scss
+++ b/gtk/theme/Adwaita/_drawing.scss
@@ -480,32 +480,6 @@
   }
 }
 
- mixin trough($flat:false, $c:$bg_color, $tc:$fg_color, $noedge:true) {
-  color: mix($tc, $bg_color, 80%);
-  @if $flat { background-image: linear-gradient(to bottom, $c); }
-  @else {
-    background-image: linear-gradient(to bottom,
-                                      mix(black,$c,15%) 5%,
-                                      mix(black,$c,10%) 20%,
-                                      mix(black,$c,10%) 90%,
-                                      $c);
-  }
-
-  border-color: if($c!=$bg_color, _border_color($c), $border_color);
-
-  @if not($noedge) {
-    @if lightness($c) > 60% {
-      box-shadow: inset 0 -1px $borders_edge,
-                  0 1px $borders_edge;
-    }
-    @else {
-      box-shadow: inset 0 -1px transparentize($borders_edge, 0.5),
-                  0 1px transparentize($borders_edge, 0.5);
-    }
-  }
-  @else { box-shadow: none; }
-}
-
 @mixin headerbar_fill($c:$headerbar_color, $hc:$top_hilight) {
 //
 // headerbar fill