Move tab index and focus to radio button.

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

 // Copyright 2016 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.
 
 Polymer({
   is: 'controlled-radio-button',
 
   behaviors: [CrPolicyPrefBehavior, PrefControlBehavior],
 
   properties: {
     name: {
       type: String,
       notify: true,
     },
 
     /** @private */
     controlled_: {
       type: Boolean,
       computed: 'computeControlled_(pref.*)',
       reflectToAttribute: true,
     },
   },
 
+  listeners: {
+    'focus': 'onFocus_',
+  },
+
   /**
    * @return {boolean} Whether the button is disabled.
    * @private
    */
   computeControlled_: function() {
     return this.isPrefPolicyControlled(assert(this.pref));
   },
 
   /**
    * @param {boolean} controlled
    * @param {string} name
    * @param {chrome.settingsPrivate.PrefObject} pref
    * @return {boolean}
    * @private
    */
   showIndicator_: function(controlled, name, pref) {
     return controlled && name == Settings.PrefUtil.prefToString(pref);
   },
 
   /**
    * @param {!Event} e
    * @private
    */
   onIndicatorTap_: function(e) {
     // Disallow <controlled-radio-button on-tap="..."> when controlled.
     e.preventDefault();
     e.stopPropagation();
   },
+
+  /** Focuses the internal radio button when the row is selected. */
+  onFocus_: function() {
+    this.$.radioButton.focus();
+  },
 });