Move ProtocolExtensionManager from SessionConnector into its own class

remoting/webapp/crd/js/me2me_activity.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.
 
 /** @suppress {duplicate} */
 var remoting = remoting || {};
 
 (function() {
 
 'use strict';
@@ skipping 102 matching lines @@
   }
 };
 
 /**
  * @param {!remoting.ConnectionInfo} connectionInfo
  */
 remoting.Me2MeActivity.prototype.onConnected = function(connectionInfo) {
   // Reset the refresh flag so that the next connection will retry if needed.
   this.retryOnHostOffline_ = true;
 
+  var plugin = connectionInfo.plugin();
   if (remoting.app.hasCapability(remoting.ClientSession.Capability.CAST)) {
-    this.connector_.registerProtocolExtension(
-        new remoting.CastExtensionHandler());
+    plugin.extensions().register(new remoting.CastExtensionHandler());
   }
-  this.connector_.registerProtocolExtension(new remoting.GnubbyAuthHandler());
+  plugin.extensions().register(new remoting.GnubbyAuthHandler());
   this.pinDialog_.requestPairingIfNecessary(connectionInfo.plugin(),
                                             this.connector_);
 };
 
 remoting.Me2MeActivity.prototype.onDisconnected = function() {
   remoting.setMode(remoting.AppMode.CLIENT_SESSION_FINISHED_ME2ME);
 };
 
 /**
  * @param {!remoting.Error} error
@@ skipping 145 matching lines @@
       clientName = 'Linux';
     } else {
       console.log('Unrecognized client platform. Using navigator.platform.');
       clientName = navigator.platform;
     }
     plugin.requestPairing(clientName, onPairingComplete);
   }
 };
 
 })();