How can you save an HTML5 video from a URL to a video?

Question

On the Apple iPhone 6 page, they use a rather neat effect that animates the timeline <video>to scroll the animation / animation page. Video Source:

blob:http%3A//www.apple.com/aa45415d-063a-4fae-b2ad-9cee7764a131

Here are some libraries I work with to accomplish this:

• purl.js
• FileSaver.js

Here JSBin is loaded with the above libraries: http://jsbin.com/godaqa/1/edit?js,console

Sidenote: What are the benefits of using a blob file as a source?