This add support for data-binding of some properties of the paper-datatable-column element (header, tooltip, and sortable).
The main reason for this is to be able to use the new localization features of Polymer (Polymer.AppLocalizeBehavior).
Code like this now works:
<paper-datatable data="{{data}}">
<paper-datatable-column header="[[localize('description')]]" property="description"></paper-datatable-column>
</paper-datatable>