https://twitter.com/left_pad/status/847911365645938690 Ref #84 TL;DR: automatically add polyfills based on actual usage in the file (check the presence of Promise), and remove any polyfills supported by the target environment (Chrome 55 already supports Promise). Check the tests in this pr for more examples! Size savings: if you don't use any polyfills in your code: then none will be added. If you