Improper calculated size of rendered elements

Sometimes dimensions returned in item.rendered property are incorrect. This is probably because childrenSize lib goes only one element deep into the tree.

Live example: http://jsfiddle.net/d1vyyvnr/

Refresh it a couple of times (ads are randomized) - sometimes height is calculated to 17px, while visually it's clearly more than that.

Env: Chrome 37.0.2062.120 on Windows 7