Update from https://crrev.com/316786

third_party/harfbuzz-ng/src/hb-open-type-private.hh

 /*
  * Copyright © 2007,2008,2009,2010  Red Hat, Inc.
  * 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
@@ skipping 176 matching lines @@
   inline void init (hb_blob_t *b)
   {
     this->blob = hb_blob_reference (b);
     this->writable = false;
   }
 
   inline void start_processing (void)
   {
     this->start = hb_blob_get_data (this->blob, NULL);
     this->end = this->start + hb_blob_get_length (this->blob);
+    assert (this->start <= this->end); /* Must not overflow. */
     this->edit_count = 0;
     this->debug_depth = 0;
 
     DEBUG_MSG_LEVEL (SANITIZE, start, 0, +1,
                      "start [%p..%p] (%lu bytes)",
                      this->start, this->end,
                      (unsigned long) (this->end - this->start));
   }
 
   inline void end_processing (void)
@@ skipping 791 matching lines @@
     }
     return -1;
   }
 };
 
 
 } /* namespace OT */
 
 
 #endif /* HB_OPEN_TYPE_PRIVATE_HH */