[HBD] Update MD SiteSettingsHandler to support 3 modes.

chrome/test/data/webui/settings/test_site_settings_prefs_browser_proxy.js

Index: chrome/test/data/webui/settings/test_site_settings_prefs_browser_proxy.js
diff --git a/chrome/test/data/webui/settings/test_site_settings_prefs_browser_proxy.js b/chrome/test/data/webui/settings/test_site_settings_prefs_browser_proxy.js
index 11b7a60200de156e91118232c97671f21a0cb46c..0402e1dd5a5d71bbe9b792b4b7426fd2965f1b2b 100644
--- a/chrome/test/data/webui/settings/test_site_settings_prefs_browser_proxy.js
+++ b/chrome/test/data/webui/settings/test_site_settings_prefs_browser_proxy.js
@@ -127,7 +127,7 @@ TestSiteSettingsPrefsBrowserProxy.prototype = {
     }
 
     assert(pref != undefined, 'Pref is missing for ' + contentType);
-    return Promise.resolve(pref != 'block');
+    return Promise.resolve(pref);
   },
 
   /** @override */