MD Settings: compose a <paper-radio-button> instead of wrapping one in <controlled-radio-button>

chrome/browser/resources/settings/controls/settings_radio_group.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview
  * `cr-radio-group` wraps a radio-group and set of radio-buttons that control
  *  a supplied preference.
  *
  * Example:
@@ skipping 10 matching lines @@
     /**
      * IronSelectableBehavior selected attribute.
      */
     selected: {
       type: String,
       notify: true,
       observer: 'selectedChanged_'
     },
   },
 
+  hostAttributes: {
+    role: 'none',
+  },
+
   observers: [
     'prefChanged_(pref.*)',
   ],
 
   /** @private */
   prefChanged_: function() {
     var pref = /** @type {!chrome.settingsPrivate.PrefObject} */(this.pref);
     this.selected = Settings.PrefUtil.prefToString(pref);
   },
 
   /** @private */
   selectedChanged_: function(selected) {
     if (!this.pref)
       return;
     this.set('pref.value',
              Settings.PrefUtil.stringToPrefValue(selected, this.pref));
   },
 });