Need option to override default "tap closes" option on core-dropdown-base

[mwinters-stuff]

Core dropdown base implements a on-tap which toggles the overlay, this should be disabled by an attribute as if you have buttons or other tappable components in the overlay, the overlay closes..

I had to override with

  ready: function(){
        this.$.menu_popup.toggleOverlay = function(){};
      },

where menu_popup is the core-dropdown-base

[morethanreal]

Fixed in 53abf8d