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

content/browser/appcache/appcache_url_request.cc

Index: content/browser/appcache/appcache_url_request.cc
diff --git a/content/browser/appcache/appcache_url_request.cc b/content/browser/appcache/appcache_url_request.cc
index 56d36ce0119e208952b5412046e25219c0593721..da320b4b21fe69c9fd1123d285da8a81baa13aa6 100644
--- a/content/browser/appcache/appcache_url_request.cc
+++ b/content/browser/appcache/appcache_url_request.cc
@@ -58,6 +58,10 @@ net::URLRequest* AppCacheURLRequest::GetURLRequest() {
   return url_request_;
 }
 
+AppCacheURLRequest* AppCacheURLRequest::AsURLRequest() {
+  return this;
+}
+
 AppCacheURLRequest::AppCacheURLRequest(net::URLRequest* url_request)
     : url_request_(url_request) {}