IFrameControl.setReferrerPolicy
        Set the referer policy attribute for the IFrame element.
 no-referrer: The Referrer header will not be sent
 no-referrer-when-downgrade: The Referrer header will not be sent to origins with HTTPS
 origin: The sent referrer will be limited to the origin of the referring page.
 origin-when-cross-origin: The referrer sent to other origins will be limited to the scheme, the host, and the port.
 same-origin: A referrer will be sent for the same origin.
 strict-origin: Only send the origin of the document as the referrer when the protocol security level stays the same (http->https), but don't send it to a less secure destination (https->http).
 strict-origin-when-cross-origin: Send a full URL when performing a same-origin request, only send the origin when the protocol security level stays the same (http->https), and send no header to a less secure destination (https->http).
 unsafe-url: The referrer will include the origin and the path