[Chromoting] Add ClientSession.Capability to enable Gnubby-based auth.

remoting/webapp/crd/js/client_session.js

 // Copyright (c) 2012 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.
 
 /**
  * @fileoverview
  * Class handling creation and teardown of a remoting client session.
  *
  * The ClientSession class controls lifetime of the client plugin
  * object and provides the plugin with the functionality it needs to
@@ skipping 367 matching lines @@
 
   // Let the host know that we're interested in knowing whether or not it
   // rate limits desktop-resize requests.
   RATE_LIMIT_RESIZE_REQUESTS: 'rateLimitResizeRequests',
 
   // Indicates that the client supports the video frame-recording extension.
   VIDEO_RECORDER: 'videoRecorder',
 
   // Indicates that the client supports 'cast'ing the video stream to a
   // cast-enabled device.
-  CAST: 'casting'
+  CAST: 'casting',
+
+  // When enabled, this capability results in the client informing the host
+  // that it supports Gnubby-based authentication.
+  GNUBBY_AUTH: 'gnubbyAuth'
 };
 
 /**
  * The set of capabilities negotiated between the client and host.
  * @type {Array.<string>}
  * @private
  */
 remoting.ClientSession.prototype.capabilities_ = null;
 
 /**
@@ skipping 1137 matching lines @@
     console.error('Received unexpected gnubby message');
   }
 };
 
 /**
  * Create a gnubby auth handler and inform the host that gnubby auth is
  * supported.
  * @private
  */
 remoting.ClientSession.prototype.createGnubbyAuthHandler_ = function() {
-  if (this.mode_ == remoting.ClientSession.Mode.ME2ME) {
+  if (this.hasCapability_(remoting.ClientSession.Capability.GNUBBY_AUTH) &&
+      this.mode_ == remoting.ClientSession.Mode.ME2ME) {
     this.gnubbyAuthHandler_ = new remoting.GnubbyAuthHandler(this);
     // TODO(psj): Move to more generic capabilities mechanism.
     this.sendGnubbyAuthMessage({'type': 'control', 'option': 'auth-v1'});
   }
 };
 
 /**
  * @return {{width: number, height: number}} The height of the window's client
  *     area. This differs between apps v1 and apps v2 due to the custom window
  *     borders used by the latter.
@@ skipping 104 matching lines @@
  * @param {string} data Contents of the extension message.
  * @return {boolean} True if the message was recognized, false otherwise.
  */
 remoting.ClientSession.prototype.handleExtensionMessage =
     function(type, data) {
   if (this.videoFrameRecorder_) {
     return this.videoFrameRecorder_.handleMessage(type, data);
   }
   return false;
 }