Missing header 'Upgrade-Insecure-Requests'
Some websites, even if the are accessed through 'https', will return 'location' headers, for redirections, which are not 'https' (http only then). This will raise a BrowserHTTPSDowngrade error.
By using 'Upgrade-Insecure-Requests' header in the requests, we can avoid such a situation. I don't know at what level this should be handled :
Also, should this header be sent only for https domains ?