Smart name removal deletes essential code from web animations next polyfill

The smart name removal pass removes an IIFE in the web-animations-next polyfill which has the side effect of polyfilling Element.prototype.animate in this [non-minified code snippet](https://github.com/web-animations/web-animations-js/blob/8a3bb632f39f8b5072c77a502eb43e880b08d94c/src/element-animatable.js#L16). This was seen when compiling the minified library which lives [here](https://github.com/web-animations/web-animations-js/blob/master/web-animations-next.min.js).