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

content/browser/appcache/appcache_request_handler.h

Index: content/browser/appcache/appcache_request_handler.h
diff --git a/content/browser/appcache/appcache_request_handler.h b/content/browser/appcache/appcache_request_handler.h
index da797b9219f542aed3d4bf75ec438b06f6bd3638..24ee0fcc7456cbd50af6d75a4c43e522325a6630 100644
--- a/content/browser/appcache/appcache_request_handler.h
+++ b/content/browser/appcache/appcache_request_handler.h
@@ -124,6 +124,10 @@ class CONTENT_EXPORT AppCacheRequestHandler
   std::unique_ptr<AppCacheJob> CreateJob(
       net::NetworkDelegate* network_delegate);
 
+  // Helper method to create an AppCacheJob for fallback responses.
+  std::unique_ptr<AppCacheJob> MaybeCreateJobForFallback(
+      net::NetworkDelegate* network_delegate);
+
   // Helper to retrieve a pointer to the storage object.
   AppCacheStorage* storage() const;