[Fetch API] Put body members directly on Response/Request

Source/modules/serviceworkers/Request.idl

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // http://fetch.spec.whatwg.org/#request-class
 
 enum RequestMode { "same-origin", "no-cors", "cors" };
 enum RequestCredentials { "omit", "same-origin", "include" };
 
 [
     Constructor(ScalarValueString input, optional Dictionary requestInitDict),
     Constructor(Request input, optional Dictionary requestInitDict),
     ConstructorCallWith=ExecutionContext,
     RuntimeEnabled=ServiceWorker,
     Exposed=ServiceWorker,
     RaisesException=Constructor,
     GarbageCollected,
 ] interface Request {
     readonly attribute ByteString method;
     readonly attribute ScalarValueString url;
     readonly attribute Headers headers;
-    [CallWith=ExecutionContext] readonly attribute FetchBodyStream body;
 
     readonly attribute DOMString referrer;
     readonly attribute RequestMode mode;
     readonly attribute RequestCredentials credentials;
 
     // FIXME: Implement the following:
     // readonly attribute RequestContext context;
 };
+
+Request implements Body;