Use dom-if to hide settings pages and show explicitly.

chrome/browser/resources/settings/site_settings/site_settings_behavior.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 Behavior common to Site Settings classes.
  */
 
 /** @polymerBehavior */
 var SiteSettingsBehaviorImpl = {
+  properties: {
+    /**
+     * The ID of the category this element is displaying data for.
+     */
+    category: {
+      type: Number,
+    },
+  },
+
   /**
    * Returns whether the category default is set to enabled or not.
    * @param {number} category The category to check.
    * @return {boolean} True if the category default is set to enabled.
    * @protected
    */
   isCategoryAllowed: function(category) {
     var pref = this.getPref(this.computeCategoryPrefName(category));
 
     // FullScreen is Allow vs. Ask.
@@ skipping 195 matching lines @@
             loadTimeData.getString('siteSettingsBlocked');
       default:
         assertNotReached();
         return '';
     }
   },
 };
 
 /** @polymerBehavior */
 var SiteSettingsBehavior = [PrefsBehavior, SiteSettingsBehaviorImpl];