Fetch API: Add Request#cache attribute

third_party/WebKit/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.
 
 // https://fetch.spec.whatwg.org/#request-class
 
 typedef (Request or USVString) RequestInfo;
 
 enum RequestMode { "navigate", "same-origin", "no-cors", "cors" };
 enum RequestCredentials { "omit", "same-origin", "include" };
 enum RequestRedirect { "follow", "error", "manual" };
+enum RequestCache { "default", "no-store", "reload", "no-cache", "force-cache", 
+    "only-if-cached" };
 
 // https://w3c.github.io/webappsec-referrer-policy/#referrer-policies
 
 enum ReferrerPolicy {
     "",
     "no-referrer",
     "no-referrer-when-downgrade",
     "origin",
     "origin-when-cross-origin",
     "unsafe-url"
 };
 
 [
     ActiveScriptWrappable,
     Constructor(RequestInfo input, optional Dictionary requestInitDict),
     ConstructorCallWith=ScriptState,
     Exposed=(Window,Worker),
     RaisesException=Constructor,
     DependentLifetime,
 ] interface Request {
     readonly attribute ByteString method;
     readonly attribute USVString url;
     [ImplementedAs=getHeaders] readonly attribute Headers headers;
     readonly attribute DOMString referrer;
     [ImplementedAs=getReferrerPolicy] readonly attribute ReferrerPolicy referrerPolicy;
     readonly attribute RequestMode mode;
     readonly attribute RequestCredentials credentials;
+    [RuntimeEnabled=FetchRequestCache]readonly attribute RequestCache cache;
     readonly attribute RequestRedirect redirect;
     readonly attribute DOMString integrity;
 
     [RaisesException, CallWith=ScriptState] Request clone();
 };
 
 Request implements Body;