Referrer not hidden when comming from a .onion address

In TorBroswer 7.0a4, when leaving a .onion page for a clearnet page, the .onion address is sent as referrer.

This should not be the case and has originally been disabled with this commit and appears to have been uplifted to Firefox since. The network.http.referer.hideOnionSource preference is set to true but seems to have no effect.

Steps to reproduce:

1. Go to duckduckgo's onion page
2. enter any search term
3. click on one of the result
4. open the inspector observe the .onion referrer being send to the target page

Trac:
Username: pege