If you add generated content (using '::before' or '::after' pseudo-elements) to child element C of parent element P, then remove it, padding of P is affected. See URL. If you scroll to the bottom, hover over an item, then mouse out, the bottom padding disappears. It may re-appear on subsequent layouts.
Confirmed in WebKit Nightly, Version 5.1.2 (6534.52.7, r109280).