Conditionally Load WC Polyfill

conditional-polyfill.js

var webComponentsSupported = ('registerElement' in document
  && 'import' in document.createElement('link')
  && 'content' in document.createElement('template'));

if (!webComponentsSupported) {
  var wcPoly = document.createElement('script');
  wcPoly.src = '/bower_components/webcomponentsjs/webcomponents-lite.js';
  wcPoly.async = true;
  (document.head || document.getElementsByTagName("head")[0]).appendChild(wcPoly);
}