Work around CancelableCompletionCallback threading restrictions.

webkit/appcache/appcache_quota_client.h

Index: webkit/appcache/appcache_quota_client.h
===================================================================
--- webkit/appcache/appcache_quota_client.h	(revision 123798)
+++ webkit/appcache/appcache_quota_client.h	(working copy)
@@ -65,6 +65,7 @@
   void ProcessPendingRequests();
   void DeletePendingRequests();
   const AppCacheStorage::UsageMap* GetUsageMap();
+  net::CancelableCompletionCallback* GetServiceDeleteCallback();
 
   // For use by appcache internals during initialization and shutdown.
   APPCACHE_EXPORT void NotifyAppCacheReady();
@@ -78,7 +79,7 @@
   // And once it's ready, we can only handle one delete request at a time,
   // so we queue up additional requests while one is in already in progress.
   DeletionCallback current_delete_request_callback_;
-  net::CancelableCompletionCallback service_delete_callback_;
+  scoped_ptr<net::CancelableCompletionCallback> service_delete_callback_;
 
   AppCacheService* service_;
   bool appcache_is_ready_;