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

content/browser/appcache/appcache_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_request.h"
 #include "content/common/appcache_interfaces.h"
 #include "net/url_request/url_request.h"
 
 namespace content {
 
 AppCacheRequest::~AppCacheRequest() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 }
 
 // static
 bool AppCacheRequest::IsSchemeAndMethodSupportedForAppCache(
     const AppCacheRequest* request) {
   return IsSchemeSupportedForAppCache(request->GetURL()) &&
          IsMethodSupportedForAppCache(request->GetMethod());
 }
 
 net::URLRequest* AppCacheRequest::GetURLRequest() {
   return nullptr;
 }
 
 ResourceRequest* AppCacheRequest::GetResourceRequest() {
   return nullptr;
 }
 
+AppCacheURLRequest* AppCacheRequest::AsURLRequest() {
+  return nullptr;
+}
+
+AppCacheURLLoaderRequest* AppCacheRequest::AsURLLoaderRequest() {
+  return nullptr;
+}
+
 }  // namespace content