At present, it is not possible to enter the URL source for
OpenLayers.js using // before the domain name (RFC 1808, Section 4) which allows the browser to determine which protocol to use to retreive the file (HTTPS / HTTP). eg.
While openlayers.org itself does not support HTTPS (eg. https://openlayers.org/dev/OpenLayers.js), we use a file from our CDN which does support HTTPS.