Fix unsafe shape_plan->face dependency

third_party/harfbuzz-ng/src/hb-shape-plan-private.hh

 /*
  * Copyright © 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
  * above copyright notice and the following two paragraphs appear in
  * all copies of this software.
@@ skipping 21 matching lines @@
 #include "hb-object-private.hh"
 #include "hb-shaper-private.hh"
 
 
 struct hb_shape_plan_t
 {
   hb_object_header_t header;
   ASSERT_POD ();
 
   hb_bool_t default_shaper_list;
-  hb_face_t *face;
+  hb_face_t *face_unsafe; /* We don't carry a reference to face. */
   hb_segment_properties_t props;
 
   hb_shape_func_t *shaper_func;
   const char *shaper_name;
 
   struct hb_shaper_data_t shaper_data;
 };
 
 #define HB_SHAPER_DATA_CREATE_FUNC_EXTRA_ARGS \
         , const hb_feature_t            *user_features \
         , unsigned int                   num_user_features
 #define HB_SHAPER_IMPLEMENT(shaper) HB_SHAPER_DATA_PROTOTYPE(shaper, shape_plan);
 #include "hb-shaper-list.hh"
 #undef HB_SHAPER_IMPLEMENT
 #undef HB_SHAPER_DATA_CREATE_FUNC_EXTRA_ARGS
 
 
 #endif /* HB_SHAPE_PLAN_PRIVATE_HH */