HTTP static pages served to HTTPS resulting in mixed content issues

Reported via w.org slack: https://wordpress.slack.com/archives/core-images/p1458158727000084
supercache creates files for both protocols, i.e. if you go to the home page of a site on http, SC creates index.html, and if you visit using ssl, then you get index-https.html

but for posts/pages not the home page, if you first visit the site on http it creates /sitename/pagename/index.html

and if you then visit on https it ​_doesn’t_​ create another file, it just serves the http version

so all of your assets get blocked

Start by reproducing the HTTP-then-HTTPS page request sequence described in the issue and inspect how Super Cache chooses the cached path for non-home pages. Done means an HTTPS request does not serve the HTTP-generated page or its blocked assets, while the existing home-page protocol behavior remains intact.

Written by the indexing model from the issue text.