Roll HarfBuzz to 1.4.6

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

 /*
  * Copyright © 2012,2013  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 293 matching lines @@
                             hb_font_t *font,
                             hb_buffer_serialize_format_t format,
                             hb_buffer_serialize_flags_t flags)
 {
   assert (start <= end && end <= buffer->len);
 
   unsigned int sconsumed;
   if (!buf_consumed)
     buf_consumed = &sconsumed;
   *buf_consumed = 0;
+  if (buf_size)
+    *buf = '\0';
 
   assert ((!buffer->len && buffer->content_type == HB_BUFFER_CONTENT_TYPE_INVALID) ||
           buffer->content_type == HB_BUFFER_CONTENT_TYPE_GLYPHS);
 
   if (!buffer->have_positions)
     flags |= HB_BUFFER_SERIALIZE_FLAG_NO_POSITIONS;
 
   if (unlikely (start == end))
     return 0;
 
@@ skipping 121 matching lines @@
       return _hb_buffer_deserialize_glyphs_json (buffer,
                                                  buf, buf_len, end_ptr,
                                                  font);
 
     default:
     case HB_BUFFER_SERIALIZE_FORMAT_INVALID:
       return false;
 
   }
 }