Steps to reproduce: 1. open any page with <video controls> 2. press on the play/pause button 3. notice how the icon shrinks a little (as set via a :active style) 4. stop pressing on the play/pause button 5. notice how the icon is still shrunk 6. mouse your mouse 7. notice how everything is back as expected I've reduced the issue in https://bugs.webkit.org/show_bug.cgi?id=174562.
<rdar://problem/33340175>