Pass error messages from native messaging to web-app.

remoting/webapp/crd/js/host_daemon_facade.js

 // Copyright 2014 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 to communicate with the host daemon via Native Messaging.
  */
 
 'use strict';
@@ skipping 178 matching lines @@
   var reply = this.pendingReplies_[id];
   if (!reply) {
     console.error('NativeMessaging: unexpected id: ', id);
     return;
   }
   delete this.pendingReplies_[id];
 
   try {
     var type = base.getStringAttr(message, 'type');
     if (type != reply.type) {
-      throw 'Expected reply type: ' + reply.type + ', got: ' + type;
+      throw new Error('Expected reply type: ' + reply.type + ', got: ' + type);
+    }
+    var error_message = base.getStringAttr(message, 'error_message', '');
+    if (error_message) {
+      var error_location = base.getStringAttr(message, 'error_location',
+                                              '<unknown>')
+      console.error(error_message + ' at ' + error_location);
     }
     reply.deferred.resolve(message);
   } catch (/** @type {*} */ e) {
     console.error('Error while processing native message', e);
     reply.deferred.reject(remoting.Error.unexpected());
   }
 };
 
 /**
  * @return {void} Nothing.
@@ skipping 268 matching lines @@
     authorizationCode: authorizationCode
   }).then(function(reply) {
     var refreshToken = base.getStringAttr(reply, 'refreshToken');
     if (refreshToken) {
       return refreshToken
     } else {
       throw remoting.Error.unexpected('Missing refreshToken');
     }
   });
 };