Use RevocableStore to isolate the http cache from its transactions....

net/http/http_cache.h

Index: net/http/http_cache.h
===================================================================
--- net/http/http_cache.h	(revision 9641)
+++ net/http/http_cache.h	(working copy)
@@ -164,6 +164,8 @@
   typedef base::hash_map<std::string, int> PlaybackCacheMap;
   scoped_ptr<PlaybackCacheMap> playback_cache_map_;
 
+  RevocableStore transactions_;
+
   DISALLOW_COPY_AND_ASSIGN(HttpCache);
 };