MD Settings: Fix subpage visibility and add appearance page tests

chrome/browser/resources/settings/privacy_page/privacy_page.js

Index: chrome/browser/resources/settings/privacy_page/privacy_page.js
diff --git a/chrome/browser/resources/settings/privacy_page/privacy_page.js b/chrome/browser/resources/settings/privacy_page/privacy_page.js
index c9a025b3a5eab8e93e2dc65d7e1afd4c307fe8c8..174bdcdbf2be815c94d56e3b022d65206c57155b 100644
--- a/chrome/browser/resources/settings/privacy_page/privacy_page.js
+++ b/chrome/browser/resources/settings/privacy_page/privacy_page.js
@@ -42,7 +42,12 @@ Polymer({
      * Dictionary defining page visibility.
      * @type {!PrivacyPageVisibility}
      */
-    pageVisibility: Object,
+    pageVisibility: {
+      type: Object,
+      value: function() {
+        return {};
+      },
+    },
 
     /** @private */
     isGuest_: {
@@ -150,6 +155,15 @@ Polymer({
   },
 
   /**
+   * @param {boolean|undefined} visibility
+   * @return {boolean}
+   * @private
+   */
+  showPage_: function(visibility) {
+    return visibility !== false;
+  },
+
+  /**
    * @param {Event} event
    * @private
    */