Move Fetch API releted code to modules/fetch.

Source/modules/serviceworkers/Response.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/#response-class
-
-enum ResponseType { "basic", "cors", "default", "error", "opaque" };
-
-// FIXME: Add union types: FormData and URLSearchParams
-typedef (Blob or ArrayBuffer or ArrayBufferView or USVString) BodyInit;
-
-[
-    Constructor(optional BodyInit body, optional Dictionary responseInitDict),
-    ConstructorCallWith=ExecutionContext,
-    Exposed(Window GlobalFetch, DedicatedWorker GlobalFetch, SharedWorker GlobalFetch, ServiceWorker ServiceWorker),
-    RaisesException=Constructor,
-    ActiveDOMObject,
-    GarbageCollected,
-    TypeChecking=Interface,
-] interface Response {
-    // FIXME: Implement redirect().
-    readonly attribute ResponseType type;
-    readonly attribute USVString url;
-    readonly attribute unsigned short status;
-    readonly attribute ByteString statusText;
-    readonly attribute Headers headers;
-
-    [RaisesException] Response clone();
-};
-
-Response implements Body;