[MD settings] lighter weight initializer for protocol handler enabled messages

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

 // Copyright 2016 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.
 
 /**
  * An example empty pref.
  * @type {SiteSettingsPref}
  */
 var prefsEmpty = {
   defaults: {
@@ skipping 32 matching lines @@
  * @constructor
  * @implements {settings.SiteSettingsPrefsBrowserProxy}
  * @extends {settings.TestBrowserProxy}
  */
 var TestSiteSettingsPrefsBrowserProxy = function() {
   settings.TestBrowserProxy.call(this, [
     'fetchUsbDevices',
     'fetchZoomLevels',
     'getDefaultValueForContentType',
     'getExceptionList',
-    'initializeProtocolHandlerList',
+    'observeProtocolHandlers',
+    'observeProtocolHandlersEnabledState',
     'removeProtocolHandler',
     'removeUsbDevice',
     'removeZoomLevel',
     'resetCategoryPermissionForOrigin',
     'setCategoryPermissionForOrigin',
     'setDefaultValueForContentType',
     'setProtocolDefault'
   ]);
 
   /** @private {!SiteSettingsPref} */
@@ skipping 170 matching lines @@
     this.methodCalled('fetchUsbDevices');
     return Promise.resolve(this.usbDevices_);
   },
 
   /** @override */
   removeUsbDevice: function() {
     this.methodCalled('removeUsbDevice', arguments);
   },
 
   /** @override */
-  initializeProtocolHandlerList: function() {
+  observeProtocolHandlers: function() {
     cr.webUIListenerCallback('setHandlersEnabled', true);
     cr.webUIListenerCallback('setProtocolHandlers', this.protocolHandlers_);
-    this.methodCalled('initializeProtocolHandlerList');
+    this.methodCalled('observeProtocolHandlers');
   },
 
   /** @override */
+  observeProtocolHandlersEnabledState: function() {
+    cr.webUIListenerCallback('setHandlersEnabled', true);
+    this.methodCalled('observeProtocolHandlersEnabledState');
+  },
+
+  /** @override */
   setProtocolDefault: function() {
     this.methodCalled('setProtocolDefault', arguments);
   },
 
   /** @override */
   removeProtocolHandler: function() {
     this.methodCalled('removeProtocolHandler', arguments);
   }
 };