In `.oo-ui-animation`/`.oo-ui-transition` mixins we've currently included `-ms-animation` & [[ https://msdn.microsoft.com/en-us/library/hh673535%28v=vs.85%29.aspx#specification | `-ms-transition` ]]. In the final published version of IE10 introducing CSS3 animations/transitions it supported unprefixed versions of those properties.
Citing from https://msdn.microsoft.com/en-us/library/hh772212%28v=vs.85%29.aspx
> Do not use the Microsoft vendor prefix ("-ms-") before the CSS animations properties. They are supported unprefixed in Internet Explorer 10 and later.
So //let's clean up and get rid of those//.
See also http://blogs.msdn.com/b/ie/archive/2011/11/21/adding-personality-with-css3-transitions-and-animations.aspx