Minor

src/hb-ot-shape-normalize.cc

diff --git a/src/hb-ot-shape-normalize.cc b/src/hb-ot-shape-normalize.cc
index b9834ca..0bcf7f5 100644
--- a/src/hb-ot-shape-normalize.cc
+++ b/src/hb-ot-shape-normalize.cc
@@ -269,6 +269,7 @@
     {
       /* Composes. Modify starter and carry on. */
       buffer->out_info[starter].codepoint = composed;
+      /* XXX update cluster */
       set_unicode_props (&buffer->out_info[starter], buffer->unicode);
 
       buffer->skip_glyph ();