Rename XMLHttpRequest to HttpRequest.

lib/dom/templates/html/dart2js/html_dart2js.darttemplate

 // 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.
 
 // DO NOT EDIT
 // Auto-generated dart:html library.
 
 #library('dart:html');
 
 #import('dart:isolate');
 #import('dart:json');
 
 $!GENERATED_DART_FILES
 
 #source('../../dom/src/EventListener.dart');
 #source('../../dom/src/KeyLocation.dart');
 #source('../../dom/src/KeyName.dart');
 #source('../../dom/src/ReadyState.dart');
 #source('../../dom/src/Timer.dart');
 #source('../../dom/src/_Collections.dart');
-#source('../../dom/src/_XMLHttpRequestUtils.dart');
+#source('../../dom/src/_HttpRequestUtils.dart');
 #source('../../html/src/IDBOpenDBRequest.dart');
 #source('../../html/src/Isolates.dart');
 #source('../../html/src/Measurement.dart');
 #source('../../html/src/shared_FactoryProviders.dart');
 #source('../../html/src/dart2js_DOMImplementation.dart');
 #source('../../html/src/dart2js_FactoryProviders.dart');
 #source('../../html/src/dart2js_IDBKeyRangeFactoryProvider.dart');
 #source('../../html/src/dart2js_IDBOpenDBRequestImplementation.dart');
 #source('../../html/src/dart2js_LocationWrapper.dart');
 #source('../../dom/src/dart2js_TypedArrayFactoryProvider.dart');
@@ skipping 27 matching lines @@
   return window.$dart$isolate$counter++;
 ''';
 
 // Fast path to invoke JS send port.
 _callPortSync(int id, message) {
   return JS('var', @'ReceivePortSync.dispatchCall(#, #)', id, message);
 }
 
 // TODO(vsm): Plumb this properly.
 spawnDomFunction(f) => spawnFunction(f);