Dynamically-resized iframes have been set to use HTTPS by default rather than the same protocol as current page. This is temporary measure that may be reverted if it causes problems with non-HTTPS sites.
On another note, GameTrailers has been removed from automated testing. The site should still work but I will not be warned if it breaks. GameTrailers's site is unreliable and suffers from backwards-incompatible changes. I've already spent too much time trying to keep it in working order and spending any more time on this single site would be detrimental to the rest of the add-on.