[gtk+] Adwaita: add comments

[Lapo Calamandrei <lapo src gnome org>]

commit 4188069db9d886e7e7478ce9a15d769af3adfb3d
Author: Lapo Calamandrei <calamandrei gmail com>
Date:   Thu Jan 29 11:34:01 2015 +0100

    Adwaita: add comments

 gtk/theme/Adwaita/_common.scss |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index 0c68437..ea6e20c 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -3263,6 +3263,7 @@ GtkVolumeButton.button { padding: 8px; }
 }
 
 // This is used by GtkScrolledWindow, when content is touch-dragged past boundaries.
+// This draws a box on top of the content, the size changes programmatically.
 .overshoot {
   &.top {
     @include overshoot(top);
@@ -3282,7 +3283,8 @@ GtkVolumeButton.button { padding: 8px; }
   }
 }
 
-.undershoot {  //FIXME: the dark variant needs love
+// Overflow indication, works similarly to the overshoot, the size if fixed tho.
+.undershoot { 
   &.top {
     @include undershoot(top);
   }