Replace ENABLE_OPENTYPE_VERTICAL implementation with HarfBuzz

Source/config.gni

Index: Source/config.gni
diff --git a/Source/config.gni b/Source/config.gni
index aea6ee3c210e3b67aa344614286745b6ebd3c2fc..f595275fca5182e5be2453c3a9257ed9edc358d5 100644
--- a/Source/config.gni
+++ b/Source/config.gni
@@ -84,11 +84,6 @@ if (use_openmax_dl_fft) {
   ]
 }
 
-if (!is_mac) {
-  # Mac OS X has not implemented support for ENABLE(OPENTYPE_VERTICAL) yet.
-  feature_defines_list += [ "ENABLE_OPENTYPE_VERTICAL=1" ]
-}
-
 if (use_default_render_theme) {
   feature_defines_list += [ "WTF_USE_DEFAULT_RENDER_THEME=1" ]
 }