MD Settings: disable <paper-radio-button>s inside of a <settings-radio-group> when controlled

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:
  *      <settings-radio-group pref="{{prefs.settings.foo}}"
  *          label="Foo Options." buttons="{{fooOptionsList}}">
  *      </settings-radio-group>
  */
 Polymer({
   is: 'settings-radio-group',
 
-  behaviors: [PrefControlBehavior],
+  behaviors: [CrPolicyPrefBehavior, PrefControlBehavior],
 
   properties: {
+    disabled_: {
+      observer: 'disabledChanged_',
+      type: Boolean,
+      value: false,
+    },
+
     /**
      * IronSelectableBehavior selected attribute.
      */
     selected: {
       type: String,
       notify: true,
       observer: 'selectedChanged_'
     },
   },
 
   observers: [
     'prefChanged_(pref.*)',
   ],
 
   /** @private */
   prefChanged_: function() {
+    this.disabled_ = this.isPrefPolicyControlled(this.pref);
     this.selected = Settings.PrefUtil.prefToString(
         /** @type {!chrome.settingsPrivate.PrefObject} */(this.pref));
   },
 
   /** @private */
+  disabledChanged_: function() {
+    if (this.disabled_) {

[michaelpg, 2016/06/08 19:23:16]

why does this assume policy is never reversed?

[Dan Beam, 2016/06/09 02:11:33]

it doesn't assume this, it was just trying not to stomp over a
<paper-radio-button> that's been disabled by other means.

if no component manages the disabled-ness of their <paper-radio-button>s, we're
probably fine to do disabled = false as well.

Pre-emptively changed to this (when disabled_ changes it stomps on children's
disabled attr)

+      var radioButtons = this.queryAllEffectiveChildren('paper-radio-button');
+      for (var i = 0; i < radioButtons.length; ++i) {
+        radioButtons[i].disabled = true;
+      }
+    }
+  },
+
+  /** @private */
   selectedChanged_: function(selected) {
     if (!this.pref)
       return;
     this.set('pref.value',
              Settings.PrefUtil.stringToPrefValue(selected, this.pref));
   },
 });