title: Extending template in Polymer
body: <p>I am trying to write a custom DOM helper similar to <code>dom-if</code> and <code>dom-repeat</code> which extends <code>template</code>. It takes an attribute say partial name. Based on this partial name it would make an ajax response and get actual content part of template which has Polymer data binding markup also. So it basically needs to do lazy render of content. </p>