Author: Peter Hurley
Revision Date: 2013-01-10 14:13:54 UTC

Use an ordered list to choose the appropriate system icon.
   The list is ordered by the following rules:
   1) Most unique names come first (ie, names least likely to exist in other themes)
   2) Themes with multiple matches require the desired icon name higher in the list
      than other possible matches.
   Fixes: https://bugs.launchpad.net/indicator-session/+bug/975563

   Preserves existing behavior: if the system menu's icon is missing in the current theme,
   fall back to gtk-missing-icon instead of showing no icon at all.
   Fixes: https://bugs.launchpad.net/bugs/1048348.