[util/hb-subset] Add --layout to keep GDEF/GSUB/GPOS

Will become default and option removed in the future.

util/hb-subset.cc

@@ -89,6 +89,7 @@ struct subset_consumer_t
 
   void finish (const font_options_t *font_opts)
   {
+    hb_subset_input_set_drop_layout (input, !subset_options.keep_layout);
     hb_subset_input_set_drop_hints (input, subset_options.drop_hints);
     hb_subset_input_set_desubroutinize (input, subset_options.desubroutinize);
 

util/options.cc

@@ -975,6 +975,7 @@ subset_options_t::add_options (option_parser_t *parser)
 {
   GOptionEntry entries[] =
   {
+    {"layout", 0, 0, G_OPTION_ARG_NONE,  &this->keep_layout,   "Keep OpenType Layout tables",   nullptr},
     {"no-hinting", 0, 0, G_OPTION_ARG_NONE,  &this->drop_hints,   "Whether to drop hints",   nullptr},
     {"desubroutinize", 0, 0, G_OPTION_ARG_NONE,  &this->desubroutinize,   "Remove CFF/CFF2 use of subroutines",   nullptr},
 

util/options.hh

@@ -670,6 +670,7 @@ struct subset_options_t : option_group_t
 {
   subset_options_t (option_parser_t *parser)
   {
+    keep_layout = false;
     drop_hints = false;
     desubroutinize = false;
 
@@ -678,6 +679,7 @@ struct subset_options_t : option_group_t
 
   void add_options (option_parser_t *parser);
 
+  hb_bool_t keep_layout;
   hb_bool_t drop_hints;
   hb_bool_t desubroutinize;
 };