rootPath setting won't work in 3.x

[Arthur Evans]

Currently the 3.x branch retains this code from 2.x:

window.Polymer = { rootPath: '/' };

(See the comment starting at:
https://github.com/Polymer/polymer-starter-kit/blob/3.0-preview/index.html#L64)

This will work in the SW register call that follows, but it will not set the Polymer rootPath variable like it did in 2.x. To do that, You'd need to load the settings module and manually set the property.

<script type="module">
import {rootPath} from '@polymer/polymer/lib/utils/settings.js';

rootPath = '/';

// Load and register pre-caching Service Worker
if ('serviceWorker' in navigator) {
  window.addEventListener('load', function() {
    navigator.serviceWorker.register('service-worker.js', {
      scope: Polymer.rootPath
    });
  });
}
</script>

That assumes, of course, that you can register a service worker from an ES module. Haven't tried.

[Arthur Evans]

Assuming we change this, we should also update the code in the tools/serviceworker docs on p-p.org.

[Russell Bicknell]

This should be fixed after #1112.