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

content/browser/appcache/appcache_request.h

Index: content/browser/appcache/appcache_request.h
diff --git a/content/browser/appcache/appcache_request.h b/content/browser/appcache/appcache_request.h
index 4e14d6547a53e40d856dd0065a54afd48b3dd68f..63dc5ec7384de8bced4df67e2efbf054837acdd5 100644
--- a/content/browser/appcache/appcache_request.h
+++ b/content/browser/appcache/appcache_request.h
@@ -16,6 +16,8 @@ class URLRequest;
 }
 
 namespace content {
+class AppCacheURLLoaderRequest;
+class AppCacheURLRequest;
 struct ResourceRequest;
 
 // Interface for an AppCache request. Subclasses implement this interface to
@@ -58,6 +60,14 @@ class CONTENT_EXPORT AppCacheRequest {
   static bool IsSchemeAndMethodSupportedForAppCache(
       const AppCacheRequest* request);
 
+  // Returns the underlying AppCacheURLRequest if any. This only applies to
+  // AppCache requests loaded via the URLRequest mechanism
+  virtual AppCacheURLRequest* AsURLRequest();
+
+  // Returns the underlying AppCacheURLLoaderRequest if any. This only applies
+  // to AppCache requests loaded via the URLLoader mechanism.
+  virtual AppCacheURLLoaderRequest* AsURLLoaderRequest();
+
  protected:
   friend class AppCacheRequestHandler;
   // Enables the AppCacheJob to call GetURLRequest() and GetResourceRequest().