Added isError method to remoting.Xhr.Error to check for HTTP errors.

remoting/webapp/crd/js/xhr.js

 // Copyright (c) 2011 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
  * Utility class for making XHRs more pleasant.
  */
 
 'use strict';
@@ skipping 276 matching lines @@
   this.url = xhr.responseURL;
 
   /** @private {string} */
   this.text_ = xhr.responseText || '';
 
   /** @private {*|undefined}  */
   this.json_ = undefined;
 };
 
 /**
+ * @return {boolean} True if the response code is outside the 200-299
+ *     range (i.e. success as defined by the HTTP protocol).
+ */
+remoting.Xhr.Response.prototype.isError = function() {
+  return this.status < 200 || this.status >= 300;
+};
+
+/**
  * @return {string} The text content of the response.
  */
 remoting.Xhr.Response.prototype.getText = function() {
   return this.text_;
 };
 
 /**
  * Get the JSON content of the response.  Requires acceptJson to have
  * been true in the request.
  * @return {*} The parsed JSON content of the response.
@@ skipping 38 matching lines @@
   var paramArray = [];
   for (var key in paramHash) {
     paramArray.push(encodeURIComponent(key) +
                      '=' + encodeURIComponent(paramHash[key]));
   }
   if (paramArray.length > 0) {
     return paramArray.join('&');
   }
   return '';
 };