<template is=dom-if> fails to add rows to a table if they contain <content>

[jyasskin]

Demo at http://plnkr.co/edit/adwhKJcfSxiM3tjxU6JS?p=preview.

    <table>
      <template is="dom-if" if="{{hasSpan}}">
        <tr>
          <th>Header</th><td><content select="span"></content></td>
        </tr>
      </template>
    ...

never shows the row, but replacing the <content> with anything else makes it work.

[kevinpschaaf]

May be related to #1631, will test after that fix.

[kevinpschaaf]

Will be fixed by #1816

Confirmed fix in repro case here:
http://jsbin.com/nunavo/2/edit