[MD settings] adding isNewTabPage setting radio buttons

chrome/browser/resources/settings/appearance_page/appearance_page.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.
 
-
-
 /**
  * 'cr-settings-appearance-page' is the settings page containing appearance
  * settings.
  *
  * Example:
  *
  *    <iron-animated-pages>
  *      <cr-settings-appearance-page prefs="{{prefs}}">
  *      </cr-settings-appearance-page>
  *      ... other pages ...
  *    </iron-animated-pages>
  *
  * @group Chrome Settings Elements
  * @element cr-settings-appearance-page
  */
 Polymer({
   is: 'cr-settings-appearance-page',
 
+  properties: {
+    /**
+     * Preferences state.
+     */
+    prefs: {
+      type: Object,
+      notify: true,
+    },
+
+    // prefs.homepage_is_newtabpage.value
+    isNewTabPageString_: {
+      type: String,
+      notify: true,
+      observer: 'isNewTabPageStringChanged_',
+    }
+  },
+
+  observers: [
+    'homepageIsNewTabPageChanged_(prefs.homepage_is_newtabpage.value)',
+  ],
+
   /** @override */
   attached: function() {
     // Query the initial state.
     cr.sendWithCallback('getResetThemeEnabled', undefined,
                         this.setResetThemeEnabled.bind(this));
 
     // Set up the change event listener.
     cr.addWebUIListener('reset-theme-enabled-changed',
                         this.setResetThemeEnabled.bind(this));
   },
 
-  properties: {
-    /**
-     * Preferences state.
-     */
-    prefs: {
-      type: Object,
-      notify: true,
-    },
+  /** @private */
+  homepageIsNewTabPageChanged_: function(newValue) {
+    this.isNewTabPageString = newValue ? 't' : 'f';

[Dan Beam, 2015/09/16 00:23:19]

if you change to 'true'/'false' (which is the same as true.toString() and
false.toString()), do you need this method?

[dschuyler, 2015/09/16 01:37:30]

It kinda works and kinda doesn't.  The part that doesn't work is the initial
value.  The initial value won't be set on load, but after the user clicks either
of the radio buttons, then they work fine.  This may be worth tinkering with
further, unless Steven is really going to replace it all with something that 
handles string/bool/int in a radio group (then I'd feel silly putting a lot of
time into making
something that only handles bools).

+  },
+
+  /** @private */
+  isNewTabPageStringChanged_: function(newValue) {
+    this.set('prefs.homepage_is_newtabpage.value',
+        this.isNewTabPageString == 't' ? true : false);
   },
 
   setResetThemeEnabled: function(enabled) {
     this.$.resetTheme.disabled = !enabled;
   },
 
   /** @private */
   openThemesGallery_: function() {
     window.open(loadTimeData.getString('themesGalleryUrl'));
   },
 
   /** @private */
   resetTheme_: function() {
     chrome.send('resetTheme');
   },
 });