HTML5 attributes: no error css class applied to validated element in these cases?

Hello guys.

I've built a small demo which shows the problem: http://jsfiddle.net/luisabreu/WMdLb/5/

It seems like using the html5 required attribute is not enough for getting a validation error when a field is empty. Removing the extend method comment makes it work as expected though.

Start with the linked JSFiddle demo and reproduce the behavior using an HTML5 required attribute on an empty field. Inspect how the extend method affects validation and CSS-class application; done means the validated empty element receives the expected validation error class without removing that method.

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