I noticed for the attachment on  issue 596283  comment 1 that View Source does not work. You just need to download the page and load it as a file URL (you don't need to run a web server as described in that comment, this requirement is for a different bug).

It seems Control-U just opens the same page not in view source mode. This page document.writes an iframe as the only content. Normal pages with iframes seem to work fine in view source, so something specific is going on with this page.