[gnome-builder] style: add workaround for gtk+ bug 759765

[Christian Hergert <chergert src gnome org>]

commit a6580a58a58f2ba5e619e04a646a6d5e4de2a4c6
Author: Christian Hergert <christian hergert me>
Date:   Mon Dec 21 19:30:04 2015 -0800

    style: add workaround for gtk+ bug 759765

 data/theme/Adwaita-shared.css |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)
---
diff --git a/data/theme/Adwaita-shared.css b/data/theme/Adwaita-shared.css
index 12b1927..417db75 100644
--- a/data/theme/Adwaita-shared.css
+++ b/data/theme/Adwaita-shared.css
@@ -38,3 +38,15 @@ symboltree entry {
   border-top: none;
   border-radius: 0px;
 }
+
+
+/*
+ * WORKAROUND:
+ *
+ * Currently, the separator color is wrong in GtkTextView's popup menu.
+ * See https://bugzilla.gnome.org/show_bug.cgi?id=759765
+ */
+menu separator {
+  color: alpha(@borders, 0.2);
+  background-color: alpha(@borders, 0.2);
+}