border-color doesn't work for an element that has been animated

[matsko]

If the polyfill operates on an element then the border-style value for that element cannot be set on an element after the animation has completed.

Here are the steps to reproduce the issue.

1. Make an animation run for some time that animates on the border-color style.

player = element.animate({ borderColor: 'red' }, 1000)

2. Then cancel the player at some point after 1000ms have passed

player.cancel()

3. Then try and set the styling for the element directly via node.style[val]:

node.style['border-color'] = 'black';

Doesn't work. It looks like this has to do with the fact that style.setProperty is monkeypatched and not style[prop].