, depending on scroll position. Use this
together with elements implementing `Polymer.PaperDialogBehavior`.

    <paper-dialog-impl>
      <h2>Header</h2>
      <paper-dialog-scrollable>
        Lorem ipsum...
      </paper-dialog-scrollable>
      <div class="buttons">
        <paper-button>OK</paper-button>
      </div>
    </paper-dialog-impl>

It shows a top divider after scrolling if it is not the first child in its parent container,
indicating there is more content above. It shows a bottom divider if 