Add first batch of controlled setting indicators

chrome/browser/resources/options/home_page_overlay.js

Index: chrome/browser/resources/options/home_page_overlay.js
diff --git a/chrome/browser/resources/options/home_page_overlay.js b/chrome/browser/resources/options/home_page_overlay.js
index 01a76c54b54a5c1a98ef92d73df51ceca31b053c..3955b536bb4ee1091b81f353077b1b1a7d05bcc4 100644
--- a/chrome/browser/resources/options/home_page_overlay.js
+++ b/chrome/browser/resources/options/home_page_overlay.js
@@ -38,8 +38,9 @@ cr.define('options', function() {
       SettingsDialog.prototype.initializePage.call(this);
 
       var self = this;
-      $('homepage-use-ntp').onchange = this.updateHomePageInput_.bind(this);
-      $('homepage-use-url').onchange = this.updateHomePageInput_.bind(this);
+      options.Preferences.getInstance().addEventListener(
+          'homepage_is_newtabpage',
+          this.handleHomepageIsNTPPrefChange.bind(this));
 
       var urlField = $('homepage-url-field');
       urlField.addEventListener('keydown', function(event) {
@@ -73,19 +74,22 @@ cr.define('options', function() {
 
     /** @inheritDoc */
     didShowPage: function() {
-      this.updateHomePageInput_();
       this.updateFavicon_();
     },
 
     /**
-     * Updates the state of the homepage text input. The input is enabled only
-     * if the |homepage-use-url| radio button is checked.
-     * @private
+     * Updates the state of the homepage text input and its controlled setting
+     * indicator when the |homepage_is_newtabpage| pref changes. The input is
+     * enabled only if the homepage is not the NTP. The indicator is always
+     * enabled but treats the input's value as read-only if the homepage is the
+     * NTP.
+     * @param {Event} Pref change event.
      */
-    updateHomePageInput_: function() {
+    handleHomepageIsNTPPrefChange: function(event) {
       var urlField = $('homepage-url-field');
-      var homePageUseURL = $('homepage-use-url');
-      urlField.setDisabled('radio-choice', !homePageUseURL.checked);
+      var urlFieldIndicator = $('homepage-url-field-indicator');
+      urlField.setDisabled('homepage-is-ntp', event.value.value);
+      urlFieldIndicator.readOnly = event.value.value;
     },
 
     /**