Roll harfbuzz to pick up this/NULL comparison fix.

third_party/harfbuzz-ng/src/hb-face-private.hh

 /*
  * Copyright © 2009  Red Hat, Inc.
  * Copyright © 2011  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
  * above copyright notice and the following two paragraphs appear in
@@ skipping 48 matching lines @@
   struct plan_node_t {
     hb_shape_plan_t *shape_plan;
     plan_node_t *next;
   } *shape_plans;
 
 
   inline hb_blob_t *reference_table (hb_tag_t tag) const
   {
     hb_blob_t *blob;
 
-    if (unlikely (!this || !reference_table_func))
+    if (unlikely (!reference_table_func))
       return hb_blob_get_empty ();
 
     blob = reference_table_func (/*XXX*/const_cast<hb_face_t *> (this), tag, user_data);
     if (unlikely (!blob))
       return hb_blob_get_empty ();
 
     return blob;
   }
 
   inline HB_PURE_FUNC unsigned int get_upem (void) const
@@ skipping 18 matching lines @@
 extern HB_INTERNAL const hb_face_t _hb_face_nil;
 
 #define HB_SHAPER_DATA_CREATE_FUNC_EXTRA_ARGS
 #define HB_SHAPER_IMPLEMENT(shaper) HB_SHAPER_DATA_PROTOTYPE(shaper, face);
 #include "hb-shaper-list.hh"
 #undef HB_SHAPER_IMPLEMENT
 #undef HB_SHAPER_DATA_CREATE_FUNC_EXTRA_ARGS
 
 
 #endif /* HB_FACE_PRIVATE_HH */