[ShadyCSS] Cannot load the polyfill async

I'm trying to load the polyfills conditionally, async and am not able to shim styles.

http://jsbin.com/qaxifecapa/edit?html,output works in Canary, but not in other browsers.

If you uncomment the `` tags in that jsbin that load the polyfills and replace this:

``` javascript
lazyLoadWCPolyfillsIfNecessary().then(function(events) {
if (!supportsShadowDOMV1) {
ShadyCSS.prepareTemplate(CardSwiper.template, CardSwiper.is);
}
window.customElements.define(CardSwiper.is, CardSwiper);
});
```

with:

``` javascript
ShadyCSS.prepareTemplate(CardSwiper.template, CardSwiper.is);
window.customElements.define(CardSwiper.is, CardSwiper);
```

then the demo works as expected.