bind valueattr

Author: Yvonne Yip

core-dropdown.html

@@ -67,7 +67,7 @@
     <core-icon id="arrow" icon="{{opened ? 'arrow-drop-up' : 'arrow-drop-down'}}"></core-icon>
   </div>
 
-  <core-popup-menu id="menu" relatedTarget="{{$.control}}" opened="{{opened}}" selected="{{selected}}" selectedItem="{{selectedItem}}" halign="{{halign}}" valign="{{valign}}">
+  <core-popup-menu id="menu" relatedTarget="{{$.control}}" opened="{{opened}}" selected="{{selected}}" valueattr="{{valueattr}}" selectedItem="{{selectedItem}}" halign="{{halign}}" valign="{{valign}}">
     <content></content>
   </core-popup-menu>