MD Settings: Fix subpage visibility and add appearance page tests

chrome/browser/resources/settings/privacy_page/privacy_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.
 
 /**
  * @fileoverview
  * 'settings-privacy-page' is the settings page containing privacy and
  * security settings.
  */
 (function() {
@@ skipping 132 matching lines @@
     this.browserProxy_.getSafeBrowsingExtendedReporting().then(setSber);
   },
 
   /** @protected */
   currentRouteChanged: function() {
     this.showClearBrowsingDataDialog_ =
         settings.getCurrentRoute() == settings.Route.CLEAR_BROWSER_DATA;
   },
 
   /**
+   * @param {boolean|undefined} visibility
+   * @return {boolean}
+   * @private
+   */
+  showPage_: function(visibility) {
+    return visibility !== false;
+  },
+
+  /**
    * @param {Event} event
    * @private
    */
   onDoNotTrackDomChange_: function(event) {
     if (this.showDoNotTrackDialog_)
       this.maybeShowDoNotTrackDialog_();
   },
 
   /**
    * Handles the change event for the do-not-track toggle. Shows a
@@ skipping 165 matching lines @@
                  : this.i18n('siteSettingsBlocked');
   },
 
   /** @private */
   getProtectedContentIdentifiersLabel_: function(value) {
     return value ? this.i18n('siteSettingsProtectedContentEnableIdentifiers')
                  : this.i18n('siteSettingsBlocked');
   },
 });
 })();