MD-Settings A11y: Disable radio list if all options are disabled.

third_party/polymer/v1_0/components-chromium/paper-radio-group/paper-radio-group-extracted.js

 Polymer({
     is: 'paper-radio-group',
 
     behaviors: [
       Polymer.IronMenubarBehavior
     ],
 
     hostAttributes: {
       role: 'radiogroup',
-      tabindex: 0
     },
 
     properties: {
       /**
        * Fired when the radio group selection changes.
        *
        * @event paper-radio-group-changed
        */
 
       /**
@@ skipping 80 matching lines @@
 
     _onLeftKey: function(event) {
       Polymer.IronMenubarBehaviorImpl._onLeftKey.apply(this, arguments);
       this._activateFocusedItem();
     },
 
     _onRightKey: function(event) {
       Polymer.IronMenubarBehaviorImpl._onRightKey.apply(this, arguments);
       this._activateFocusedItem();
     }
-  });
+  });