l): cannot put `slot` into properties because it is patched.
  ready: function() {
    this.slot = 'foo';
  }

});
</script>
</dom-module>

<dom-module id="x-select-attr">
  <template>
    Foo: [<slot name="foo"></slot>]
    Bar: [<slot name="bar"></slot>]
  </template>
  <script type="module">
import '../../polymer-legacy.js';
import { Polymer } from '../../lib/legacy/polymer-fn.js';
Polymer({is: 'x-select-attr'});
</script>
</dom-module>

<dom-module id="x-compose-select-attr">
  <template>
    <x-select-