Make sure the selected background color shows up for GtkIconView
widgets. The gtalk window picker relies on this.

BUG=None
TEST=Ran on alex

Change-Id: I08f78aea53babc2fb3e9a573f3549c6159e5f22f
Reviewed-on: http://gerrit.chromium.org/gerrit/8246
Reviewed-by: Daniel Erat <derat@chromium.org>
Tested-by: Noah Richards <noahric@chromium.org>
Commit-Ready: Noah Richards <noahric@chromium.org>