[1/3 blink] Support redirect option of Request and "opaqueredirect" response type.

Source/modules/fetch/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
 
 typedef (Request or USVString) RequestInfo;
 
 enum RequestContext {
     "", "audio", "beacon", "cspreport", "download", "embed", "eventsource", "favicon",
     "fetch", "font", "form", "frame", "hyperlink", "iframe", "image", "imageset", "import",
     "internal", "location", "manifest", "metarefresh", "object", "ping", "plugin",
     "prefetch", "script", "serviceworker", "sharedworker",
     "subresource", "style", "track", "video", "worker", "xmlhttprequest", "xslt"
 };
 enum RequestMode { "same-origin", "no-cors", "cors" };
 enum RequestCredentials { "omit", "same-origin", "include" };
+// TODO(horo): Support RequestRedirect when the chromium side patch land.
+// enum RequestRedirect { "follow", "error", "manual" };
 
 [
     Constructor(RequestInfo input, optional Dictionary requestInitDict),
     ConstructorCallWith=ScriptState,
     Exposed=(Window,Worker),
     RaisesException=Constructor,
     ActiveDOMObject,
     GarbageCollected,
     TypeChecking=Interface,
 ] interface Request {
     readonly attribute ByteString method;
     readonly attribute USVString url;
     readonly attribute Headers headers;
     readonly attribute RequestContext context;
     readonly attribute DOMString referrer;
     readonly attribute RequestMode mode;
     readonly attribute RequestCredentials credentials;
+    // TODO(horo): Support redirect attribute when the chromium side patch land.
+    // readonly attribute RequestRedirect redirect;
 
     [RaisesException] Request clone();
 };
 
 Request implements Body;