[MD settings] add sub-label to Show Home Button check box

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.
 
 /**
  * 'settings-appearance-page' is the settings page containing appearance
  * settings.
  *
  * Example:
  *
@@ skipping 112 matching lines @@
     // Query the initial state.
     cr.sendWithPromise('getResetThemeEnabled').then(
         this.setResetThemeEnabled.bind(this));
 
     // Set up the change event listener.
     cr.addWebUIListener('reset-theme-enabled-changed',
                         this.setResetThemeEnabled.bind(this));
   },
 
   /**
+   * @param {boolean} isNtp Whether to use the NTP as the home page.
+   * @param {string} homepage If not using NTP, use this URL.
+   * @return {string} The sub-label.
+   * @private
+   */
+  getShowHomeSubLabel_: function(isNtp, homepage) {
+    if (isNtp)
+      return this.i18n('homePageNtp');
+    return homepage || this.i18n('exampleDotCom');
+  },
+
+  /**
    * @param {boolean} enabled Whether the theme reset is available.
    */
   setResetThemeEnabled: function(enabled) {
     this.allowResetTheme_ = enabled;
   },
 
   /** @private */
   onCustomizeFontsTap_: function() {
     this.$.pages.setSubpageChain(['appearance-fonts']);
   },
@@ skipping 25 matching lines @@
    * @param {number} percent The integer percentage of the page zoom.
    * @private
    */
   zoomLevelChanged_: function(percent) {
     // The |percent| may be undefined on startup.
     if (percent === undefined)
       return;
     chrome.settingsPrivate.setDefaultZoomPercent(percent);
   },
 });