Updated XHR API so call sites are more descriptive.

remoting/webapp/crd/js/host_controller.js

Index: remoting/webapp/crd/js/host_controller.js
diff --git a/remoting/webapp/crd/js/host_controller.js b/remoting/webapp/crd/js/host_controller.js
index 1a70ccda3e9d7be56489bbaf8b90d5e0e107b55b..57c24f8ec038eae6a42c451fcb2ae1d09bb0fc76 100644
--- a/remoting/webapp/crd/js/host_controller.js
+++ b/remoting/webapp/crd/js/host_controller.js
@@ -234,14 +234,14 @@ remoting.HostController.prototype.start = function(hostPin, consent, onDone,
    * @param {string} hostName
    * @param {string} publicKey
    * @param {string} privateKey
-   * @param {XMLHttpRequest} xhr
+   * @param {remoting.Xhr.Response} xhrr
    */
   function onRegistered(
-      hostName, publicKey, privateKey, xhr) {
-    var success = (xhr.status == 200);
+      hostName, publicKey, privateKey, xhrr) {
+    var success = (xhrr.status == 200);
 
     if (success) {
-      var result = base.jsonParseSafe(xhr.responseText);
+      var result = base.jsonParseSafe(xhrr.responseText);
       if ('data' in result && 'authorizationCode' in result['data']) {
         that.hostDaemonFacade_.getCredentialsFromAuthCode(
             result['data']['authorizationCode'],
@@ -260,8 +260,8 @@ remoting.HostController.prototype.start = function(hostPin, consent, onDone,
             });
       }
     } else {
-      console.log('Failed to register the host. Status: ' + xhr.status +
-                  ' response: ' + xhr.responseText);
+      console.log('Failed to register the host. Status: ' + xhrr.status +
+                  ' response: ' + xhrr.responseText);
       onError(remoting.Error.REGISTRATION_FAILED);
     }
   }
@@ -281,16 +281,15 @@ remoting.HostController.prototype.start = function(hostPin, consent, onDone,
        publicKey: publicKey
     } };
 
-    remoting.xhr.start({
+    new remoting.Xhr({
       method: 'POST',
       url: remoting.settings.DIRECTORY_API_BASE_URL + '/@me/hosts',
       urlParams: {
         hostClientId: hostClientId
       },
-      onDone: onRegistered.bind(null, hostName, publicKey, privateKey),
       jsonContent: newHostDetails,
       oauthToken: oauthToken
-    });
+    }).then(onRegistered.bind(null, hostName, publicKey, privateKey));
   }
 
   /**