Clear disk cache when the cache is not initialized

net/http/http_cache.h

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file declares a HttpTransactionFactory implementation that can be
 // layered on top of another HttpTransactionFactory to add HTTP caching.  The
 // caching logic follows RFC 2616 (any exceptions are called out in the code).
 //
 // The HttpCache takes a disk_cache::Backend as a parameter, and uses that for
 // the cache storage.
@@ skipping 75 matching lines @@
             int cache_size);
 
   // Initialize the cache from its component parts, which is useful for
   // testing.  The lifetime of the network_layer and disk_cache are managed by
   // the HttpCache and will be destroyed using |delete| when the HttpCache is
   // destroyed.
   HttpCache(HttpTransactionFactory* network_layer,
             disk_cache::Backend* disk_cache);
 
   HttpTransactionFactory* network_layer() { return network_layer_.get(); }
-  disk_cache::Backend* disk_cache() { return disk_cache_.get(); }
+
+  // Returns the cache backend for this HttpCache instance. If the backend
+  // is not initialized yet, this method will initialize it. If the return
+  // value is NULL then the backend cannot be initialized.
+  disk_cache::Backend* GetBackend();
 
   // HttpTransactionFactory implementation:
   virtual int CreateTransaction(scoped_ptr<HttpTransaction>* trans);
   virtual HttpCache* GetCache();
   virtual HttpNetworkSession* GetSession();
   virtual void Suspend(bool suspend);
 
   // Helper function for reading response info from the disk cache.  If the
   // cache doesn't have the whole resource *|request_truncated| is set to true.
   static bool ReadResponseInfo(disk_cache::Entry* disk_entry,
@@ skipping 91 matching lines @@
   scoped_ptr<disk_cache::Backend> disk_cache_;
 
   // The set of active entries indexed by cache key
   ActiveEntriesMap active_entries_;
 
   // The set of doomed entries
   ActiveEntriesSet doomed_entries_;
 
   ScopedRunnableMethodFactory<HttpCache> task_factory_;
 
-  bool in_memory_cache_;
   bool enable_range_support_;
   int cache_size_;
 
   typedef base::hash_map<std::string, int> PlaybackCacheMap;
   scoped_ptr<PlaybackCacheMap> playback_cache_map_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpCache);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_CACHE_H_