Add support for subresource request fallback in AppCache for the network service..

content/browser/appcache/appcache_url_request.cc

 // Copyright (c) 2017 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.
 
 #include "content/browser/appcache/appcache_url_request.h"
 #include "net/url_request/url_request.h"
 
 namespace content {
 
 // static
@@ skipping 40 matching lines @@
     const std::string& name) const {
   std::string header;
   url_request_->GetResponseHeaderByName(name, &header);
   return header;
 }
 
 net::URLRequest* AppCacheURLRequest::GetURLRequest() {
   return url_request_;
 }
 
+AppCacheURLRequest* AppCacheURLRequest::AsURLRequest() {
+  return this;
+}
+
 AppCacheURLRequest::AppCacheURLRequest(net::URLRequest* url_request)
     : url_request_(url_request) {}
 
 AppCacheURLRequest::~AppCacheURLRequest() {}
 
 }  // namespace content