Optimize font fallback for Chinese fonts on Mac

ui/strings/translations/app_locale_settings_zh-TW.xtb

Index: ui/strings/translations/app_locale_settings_zh-TW.xtb
diff --git a/ui/strings/translations/app_locale_settings_zh-TW.xtb b/ui/strings/translations/app_locale_settings_zh-TW.xtb
index 7cf4c75a5302582b1089e25a3ce20f99935a9728..e666d384489f593da4b78264d6cc324d8f29f0a6 100644
--- a/ui/strings/translations/app_locale_settings_zh-TW.xtb
+++ b/ui/strings/translations/app_locale_settings_zh-TW.xtb
@@ -6,8 +6,11 @@
   <translation id="IDS_WEB_FONT_FAMILY">'Segoe UI',Arial,'Microsoft Jhenghei',sans-serif</translation>
   <translation id="IDS_WEB_FONT_FAMILY_XP">Arial,'Microsoft Jhenghei',PMingLiu,sans-serif</translation>
 </if>
-<if expr="is_macosx or is_ios">
-  <translation id="IDS_WEB_FONT_FAMILY">Helvetica,Heiti TC,sans-serif</translation>
+<if expr="is_macosx">
+  <translation id="IDS_WEB_FONT_FAMILY">system-ui,PingFang TC,Heiti TC,sans-serif</translation>
+</if>
+<if expr="is_ios">
+  <translation id="IDS_WEB_FONT_FAMILY">Helvetica,PingFang TC,Heiti TC,sans-serif</translation>
 </if>
 <if expr="desktop_linux and not chromeos">
     <translation id="IDS_WEB_FONT_FAMILY">Noto Sans CJK SC, WenQuanYi Zen Hei, sans-serif</translation>