MD Settings: circumvent problems with shadow DOM and aria radio* roles

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: [PrefControlBehavior],
 
   properties: {
-    label: String,
+    label: {
+      type: String,
+      observer: 'labelChanged_',
+    },
 
     name: {
       type: String,
       notify: true,
     },
 
     /** @private */
     controlled_: {
       type: Boolean,
       computed: 'computeControlled_(pref.*)',
       reflectToAttribute: true,
     },
   },
 
+  hostAttributes: {
+    // NOTE(dbeam): this should not be necessary but currently radiogroup and
+    // radio roles don't work across shadow DOM boundaries.
+    role: 'radio',
+  },
+
   listeners: {
     'focus': 'onFocus_',
   },
 
   /**
    * @return {boolean} Whether the button is disabled.
    * @private
    */
   computeControlled_: function() {
     return this.pref.enforcement == chrome.settingsPrivate.Enforcement.ENFORCED;
   },
 
+  /** @private */
+  labelChanged_: function() {
+    if (this.label)
+      this.setAttribute('aria-label', this.label);
+    else
+      this.removeAttribute('aria-label');

[hcarmona, 2017/04/11 17:47:25]

There's only one case where label isn't set.

https://cs.chromium.org/chromium/src/chrome/browser/resources/settings/appear...

After this change, the radio and input are unlabelled.

+  },
+
   /**
    * @param {boolean} controlled
    * @param {string} name
    * @return {boolean}
    * @private
    */
   showIndicator_: function(controlled, name) {
     return controlled &&
         name == Settings.PrefUtil.prefToString(assert(this.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();
   },
 });