Use HTTPS is a Chrome extension that will force sites to use HTTPS. It's currently based on a whitlist system: only sites on the whitelist are redirected.

Use HTTPS is incognito-safe, and will not keep any browsing history or data from incognito tabs, while preventing users from doing the same.

There is an RPC API available to other extensions to use. This way, interference can be coded against.

This is dogfood quality software. I'm using it on a daily basis, and it should work. Unless you pull a bad commit. Or find a new edge case. Or I changed something. Or...