Add internal hb_buffer_t::get_scratch_buffer()
diff --git a/src/hb-buffer-private.hh b/src/hb-buffer-private.hh
index 8f2095a..a4d7b8f 100644
--- a/src/hb-buffer-private.hh
+++ b/src/hb-buffer-private.hh
@@ -135,6 +135,8 @@
   { return likely (size <= allocated) ? TRUE : enlarge (size); }
 
   HB_INTERNAL bool make_room_for (unsigned int num_in, unsigned int num_out);
+
+  HB_INTERNAL void *get_scratch_buffer (unsigned int *size);
 };