It's not up to Google, it's up to web developers. If they find <portal> useful they'll implement it which forces FF/Safari to create their own implementations.

It's not up to Google, it's up to web developers. If they find <portal> useful they'll implement it which forces FF/Safari to create their own implementations. Dart ran natively in Chrome once. Why doesn't it now? Because webdevs didn't care enough to write native Dart on the front-end.