[ShadyCSS] App loading performance issue in Chrome <= 45

### Description
We started using WebComponents in our apps and for apps built with Chromium <= 45 we experienced app loading performance issue. Application loading time increased from 2-5 seconds to 2-5 minutes. With Chrome performance tool we found that this regex takes a lot of time: https://github.com/webcomponents/polyfills/blob/78c69a568de9a75adaf599b1146ead5787956a36/packages/shadycss/src/css-parse.js#L257

Is there any reason why we can't simplify css-property selector from `[^;:]*?` to `[\w\s\d-]*?`? It increases performance even in up-to-date browsers: https://jsbench.me/dsk62aojjg/1

### Browsers Affected

- [x] Chrome
- [ ] Firefox
- [ ] Edge
- [ ] Safari
- [ ] IE 11