Demo links in async call-stack tutorial are broken

The [async call stack](http://www.html5rocks.com/en/tutorials/developertools/async-call-stack/) tutorial links to 2 demos:

http://www.html5rocks.com/en/tutorials/speed/animations/post.html
http://www.html5rocks.com/en/tutorials/developertools/async-call-stack/past-scope/demo.html

Both links are broken.
