MD Settings: Fix subpage visibility and add appearance page tests

chrome/browser/resources/settings/privacy_page/privacy_page.html

Index: chrome/browser/resources/settings/privacy_page/privacy_page.html
diff --git a/chrome/browser/resources/settings/privacy_page/privacy_page.html b/chrome/browser/resources/settings/privacy_page/privacy_page.html
index 67000f84e486e82b579be022586d5d71fad92fe8..9da921545bb3cce73cda16446f77764ea522aa84 100644
--- a/chrome/browser/resources/settings/privacy_page/privacy_page.html
+++ b/chrome/browser/resources/settings/privacy_page/privacy_page.html
@@ -55,14 +55,15 @@
               label="$i18n{linkDoctorPref}">
           </settings-toggle-button>
         </div>
-        <div class="settings-box" hidden="[[!pageVisibility.searchPrediction]]">
+        <div class="settings-box"
+            hidden="[[!showPage_(pageVisibility.searchPrediction)]]">
           <settings-toggle-button class="start"
               pref="{{prefs.search.suggest_enabled}}"
               label="$i18n{searchSuggestPref}">
           </settings-toggle-button>
         </div>
         <div class="settings-box"
-            hidden="[[!pageVisibility.networkPrediction]]">
+            hidden="[[!showPage_(pageVisibility.networkPrediction)]]">
           <settings-toggle-button class="start"
               pref="{{prefs.net.network_prediction_options}}"
               label="$i18n{networkPredictionEnabled}"