Updated remoting.xhr API to use promises. Removed access to the native

remoting/webapp/app_remoting/js/app_remoting.js

Index: remoting/webapp/app_remoting/js/app_remoting.js
diff --git a/remoting/webapp/app_remoting/js/app_remoting.js b/remoting/webapp/app_remoting/js/app_remoting.js
index 3d3b58566dc50bdee4b5e19897d15abb322564af..46a0555461c99d09e03f15d1ea16a0e54406e6ff 100644
--- a/remoting/webapp/app_remoting/js/app_remoting.js
+++ b/remoting/webapp/app_remoting/js/app_remoting.js
@@ -104,11 +104,11 @@ remoting.AppRemoting.prototype.start = function(connector, token) {
   /** @type {remoting.AppRemoting} */
   var that = this;
 
-  /** @param {XMLHttpRequest} xhr */
-  var parseAppHostResponse = function(xhr) {
-    if (xhr.status == 200) {
+  /** @param {!remoting.Xhr.Response} xhrResponse */
+  var parseAppHostResponse = function(xhrResponse) {
+    if (xhrResponse.status == 200) {
       var response = /** @type {remoting.AppRemoting.AppHostResponse} */
-          (base.jsonParseSafe(xhr.responseText));
+          (base.jsonParseSafe(xhrResponse.getText()));
       if (response &&
           response.status &&
           response.status == 'done' &&
@@ -148,33 +148,37 @@ remoting.AppRemoting.prototype.start = function(connector, token) {
 
         connector.connectMe2App(host, fetchThirdPartyToken);
       } else if (response && response.status == 'pending') {
-        that.handleError(remoting.Error.SERVICE_UNAVAILABLE);
+        that.handleError(new remoting.Error(
+            remoting.Error.Tag.SERVICE_UNAVAILABLE));
       }
     } else {
       console.error('Invalid "runApplication" response from server.');
       // TODO(garykac) Start using remoting.Error.fromHttpStatus once it has
       // been updated to properly report 'unknown' errors (rather than
       // reporting them as AUTHENTICATION_FAILED).
-      if (xhr.status == 0) {
-        that.handleError(remoting.Error.NETWORK_FAILURE);
-      } else if (xhr.status == 401) {
-        that.handleError(remoting.Error.AUTHENTICATION_FAILED);
-      } else if (xhr.status == 403) {
-        that.handleError(remoting.Error.APP_NOT_AUTHORIZED);
-      } else if (xhr.status == 502 || xhr.status == 503) {
-        that.handleError(remoting.Error.SERVICE_UNAVAILABLE);
+      if (xhrResponse.status == 0) {
+        that.handleError(new remoting.Error(
+            remoting.Error.Tag.NETWORK_FAILURE));
+      } else if (xhrResponse.status == 401) {
+        that.handleError(new remoting.Error(
+            remoting.Error.Tag.AUTHENTICATION_FAILED));
+      } else if (xhrResponse.status == 403) {
+        that.handleError(new remoting.Error(
+            remoting.Error.Tag.APP_NOT_AUTHORIZED));
+      } else if (xhrResponse.status == 502 || xhrResponse.status == 503) {
+        that.handleError(new remoting.Error(
+            remoting.Error.Tag.SERVICE_UNAVAILABLE));
       } else {
-        that.handleError(remoting.Error.UNEXPECTED);
+        that.handleError(remoting.Error.unexpected());
       }
     }
   };
 
-  remoting.xhr.start({
+  new remoting.Xhr({
     method: 'POST',
     url: that.runApplicationUrl(),
-    onDone: parseAppHostResponse,
     oauthToken: token
-  });
+  }).start().then(parseAppHostResponse);
 };
 
 /**
@@ -332,11 +336,11 @@ remoting.AppRemoting.prototype.handleExtensionMessage = function(
  * @return {void} Nothing.
  */
 remoting.AppRemoting.prototype.handleError = function(error) {
-  console.error('Connection failed: ' + error.tag);
+  console.error('Connection failed: ' + error.toString());
   remoting.LoadingWindow.close();
   remoting.MessageWindow.showErrorMessage(
       chrome.i18n.getMessage(/*i18n-content*/'CONNECTION_FAILED'),
-      chrome.i18n.getMessage(/** @type {string} */ (error.tag)));
+      chrome.i18n.getMessage(error.getTag()));
 };
 
 /**