[subset] keep features that have FeatureParams and the tag is "size"

src/hb-ot-layout-gsubgpos.hh

@@ -3783,8 +3783,12 @@ struct GSUBGPOS
 	// http://lists.freedesktop.org/archives/harfbuzz/2012-November/002660.html
         continue;
 
-      if (f.featureParams.is_null ()
-	  && !f.intersects_lookup_indexes (lookup_indices)
+
+      if (!f.featureParams.is_null () &&
+          tag == HB_TAG ('s', 'i', 'z', 'e'))
+        continue;
+
+      if (!f.intersects_lookup_indexes (lookup_indices)
 #ifndef HB_NO_VAR
           && !alternate_feature_indices.has (i)
 #endif

test/subset/data/Makefile.am

@@ -40,6 +40,7 @@ EXTRA_DIST += \
 	expected/layout.tinos \
 	expected/layout.duplicate_features \
 	expected/layout.unsorted_featurelist \
+	expected/layout.drop_feature \
 	expected/cmap \
 	expected/cmap14 \
 	expected/sbix \

test/subset/data/Makefile.sources

@@ -38,6 +38,7 @@ TESTS = \
 	tests/layout.tinos.tests \
 	tests/layout.duplicate_features.tests \
 	tests/layout.unsorted_featurelist.tests \
+	tests/layout.drop_feature.tests \
         tests/sbix.tests \
 	tests/variable.tests \
 	tests/glyph_names.tests \

test/subset/data/tests/layout.drop_feature.tests

@@ -0,0 +1,10 @@
+FONTS:
+SpectralSC-ExtraLightItalic.ttf
+
+PROFILES:
+default.txt
+glyph-names.txt
+notdef-outline.txt
+
+SUBSETS:
+*

test/subset/meson.build

@@ -32,6 +32,7 @@ tests = [
   'layout.tinos',
   'layout.duplicate_features',
   'layout.unsorted_featurelist',
+  'layout.drop_feature',
   'cmap',
   'cmap14',
   'sbix',