Chromium roll (https://codereview.chromium.org/976353002)

third_party/harfbuzz-ng/src/hb-buffer.cc

 /*
  * Copyright © 1998-2004  David Turner and Werner Lemberg
  * Copyright © 2004,2007,2009,2010  Red Hat, Inc.
  * Copyright © 2011,2012  Google, Inc.
  *
  *  This is part of HarfBuzz, a text shaping library.
  *
  * Permission is hereby granted, without written agreement and without
  * license or royalty fees, to use, copy, modify, and distribute this
  * software and its documentation for any purpose, provided that the
@@ skipping 436 matching lines @@
     return;
 
   for (i = start, j = end - 1; i < j; i++, j--) {
     hb_glyph_info_t t;
 
     t = info[i];
     info[i] = info[j];
     info[j] = t;
   }
 
-  if (pos) {
+  if (have_positions) {
     for (i = start, j = end - 1; i < j; i++, j--) {
       hb_glyph_position_t t;
 
       t = pos[i];
       pos[i] = pos[j];
       pos[j] = t;
     }
   }
 }
 
@@ skipping 1117 matching lines @@
 
   unsigned int start = 0;
   unsigned int end;
   for (end = start + 1; end < count; end++)
     if (info[start].cluster != info[end].cluster) {
       normalize_glyphs_cluster (buffer, start, end, backward);
       start = end;
     }
   normalize_glyphs_cluster (buffer, start, end, backward);
 }