Install failure with HTTPS reverse proxy on newer browsers

I also think we need to do a little bit more to have everything covered.

Something like the patch attached.

Discussed with @catch - we feel that this is only a major (that we'd like to fix before release) because it requires that you are using a reverse proxy, https and the web installer. Probably not a common situation.

The real issue here is that the installer is not handling the request through the kernel and requires refactoring to do that. It would be a massive amount of work and not something we're going to attempt before D8 release.

As a workaround, this may help. You can set environment variables in Apache, for example, by having the proxy send X-Forwarded-Proto = https:

# This helps applications behind a proxy know that the pages
# were originally requested over https

SetEnvIf X-Forwarded-Proto https HTTPS=on

Committed/pushed to 8.0.x, thanks!

This one bit me with nginx and php-fpm.
After trying to install head I still was getting mixed content warnings from Firefox, and thus no theme.
This fixed it for me on nginx

fastcgi_param HTTPS $https;