[gnome-shell-sass] add note about app icon sizing

[Jakub Steiner <jimmac src gnome org>]

commit eb29ab580d569075f0208074383690f107b3e6dd
Author: Jakub Steiner <jimmac gmail com>
Date:   Wed Jul 8 18:08:34 2015 +0200

    add note about app icon sizing
    
    https://bugzilla.gnome.org/show_bug.cgi?id=747932

 _common.scss |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/_common.scss b/_common.scss
index 3abb6ed..ee80092 100644
--- a/_common.scss
+++ b/_common.scss
@@ -669,6 +669,7 @@ StScrollBar {
       -st-icon-style: symbolic;
       margin-left: 4px;
       margin-right: 4px;
+      //dimensions of the icon are hardcoded
     }
 
     &:hover {