[css-animations] Consider accept string for animation name for compatibility?

I raised this on the Compatibility spec [1], but I guess it's also worth
mentioning this here.

It seems to me @-webkit-keyframes and -webkit-animation-name in WebKit and
Blink accept an arbitrary string as animation name. And WebKit even
supports this for unprefixed @keyframes and animation-name as well.

I wonder whether we should add this to this (CSS Animation) spec in
additional to <custom-ident>, or just have the Compatibility spec say
webkit-prefixed ones should accept strings.

Thoughts?


[1] https://github.com/whatwg/compat/issues/43

- Xidorn