Rename XMLHttpRequest to HttpRequest.

lib/dom/templates/html/interface/interface_XMLHttpRequest.darttemplate

Index: lib/dom/templates/html/interface/interface_XMLHttpRequest.darttemplate
===================================================================
--- lib/dom/templates/html/interface/interface_XMLHttpRequest.darttemplate	(revision 10850)
+++ lib/dom/templates/html/interface/interface_XMLHttpRequest.darttemplate	(working copy)
@@ -1,12 +0,0 @@
-// Copyright (c) 2011, 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.
-
-// WARNING: Do not edit - generated code.
-
-$!COMMENT
-interface $ID$EXTENDS {
-  $ID.get(String url, onSuccess($ID request));
-
-  $ID.getWithCredentials(String url, onSuccess($ID request));
-$!MEMBERS}