I'm on latest Chrome, OS X and get this error:
[blocked] The page at 'https://dl.dropboxusercontent.com/u/14376395/html/proxy.html' was loaded over HTTPS, but ran insecure content from 'http://jpillora.com/xdomain/dist/0.6/xdomain.js': this content should also be loaded over HTTPS.
I'm on latest Chrome, OS X and get this error: