In this case, there's no protocol version that we can extract for
nsIHttpChannel.
The code that does the redirect is here: 7f3d9fce41/docshell/base/nsDocShell.cpp (L6079-L6095)
To trigger this codepath, we'd need to run test inside a special
docker container that has https server running on the 443 port. We lack
infrastructure for this kind of tests (but it'll be cool to have it).
References #11118
When Firefox decides to perform an http->https redirect based on HSTS
information, it issues an "internal" redirect and cancels the http request.
Since there is no response for the http request, we forge 307 redirect
in this case, following Chromium lead.
The relevant code is in nsHttpChannel::StartRedirectChannelToHttps.
