Template content doesn't render in snippet on Firefox

[tstewart15]

Here's a demo-snippet on Chrome:

Here's the same demo-snippet on Firefox:

Notice the template content doesn't show up in the snippet on Firefox.

[notwaldorf]

Oof, I think this is a known problem of the webcomponents polyfill. See: webcomponents/webcomponentsjs#362 or webcomponents/webcomponentsjs#498.

I tried to fix this in #6 but it was really messy, so I don't think this will work right :(