[gnome-themes-standard] Add a stub style for the dragged treeview column header

[Cosimo Cecchi <cosimoc src gnome org>]

commit 7b3dac1115cb4d6eef366743a7b330788922fed8
Author: Stefano Facchini <stefano facchini gmail com>
Date:   Thu Sep 27 19:07:24 2012 +0200

    Add a stub style for the dragged treeview column header
    
    https://bugzilla.gnome.org/show_bug.cgi?id=684982

 themes/Adwaita/gtk-3.0/gtk-widgets.css |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/themes/Adwaita/gtk-3.0/gtk-widgets.css b/themes/Adwaita/gtk-3.0/gtk-widgets.css
index d6c3779..b0adf55 100644
--- a/themes/Adwaita/gtk-3.0/gtk-widgets.css
+++ b/themes/Adwaita/gtk-3.0/gtk-widgets.css
@@ -3064,6 +3064,16 @@ column-header .button *:active:hover {
     icon-shadow: none;
 }
 
+column-header.dragged-header,
+column-header .dragged-header {
+    /* FIXME */
+    color: black;
+    background-color: transparent;
+    background-image: linear-gradient(to bottom,
+                                       alpha(shade(@theme_base_color, 0.7), 0.8) 15%,
+                                       alpha(@theme_base_color, 0.8));
+}
+
 row:hover {
     border-width: 0;
 }