Rename XMLHttpRequest to HttpRequest.

lib/dom/src/_HttpRequestUtils.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-class _XMLHttpRequestUtils {
+class _HttpRequestUtils {
 
-  // Helper for factory XMLHttpRequest.get
-  static XMLHttpRequest get(String url,
-                            onSuccess(XMLHttpRequest request),
+  // Helper for factory HttpRequest.get
+  static HttpRequest get(String url,
+                            onSuccess(HttpRequest request),
                             bool withCredentials) {
-    final request = new XMLHttpRequest();
+    final request = new HttpRequest();
     request.open('GET', url, true);
 
     request.withCredentials = withCredentials;
 
     // Status 0 is for local XHR request.
     request.on.readyStateChange.add((e) {
-      if (request.readyState == XMLHttpRequest.DONE &&
+      if (request.readyState == HttpRequest.DONE &&
           (request.status == 200 || request.status == 0)) {
         onSuccess(request);
       }
     });
 
     request.send();
 
     return request;
   }
 }