Animate the CSS Height and absolutely positioned element

[knyttr]

1. Suppose we have a <div> with another element which is absolutely positioned to the bottom of the <div>
2. When we animate the height of the <div>, the absolutely positioned element disappears during the animation.
3. Demonstration can be seen on: ​http://vojte.cz/test.html

[dmethvin]

Dup of #5767.