Virtual destructors should have virtual keyword.

net/disk_cache/backend_impl.h

 // Copyright (c) 2011 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.
 
 // See net/disk_cache/disk_cache.h for the public interface of the cache.
 
 #ifndef NET_DISK_CACHE_BACKEND_IMPL_H_
 #define NET_DISK_CACHE_BACKEND_IMPL_H_
 #pragma once
 
@@ skipping 29 matching lines @@
 // This class implements the Backend interface. An object of this
 // class handles the operations of the cache for a particular profile.
 class NET_TEST BackendImpl : public Backend {
   friend class Eviction;
  public:
   BackendImpl(const FilePath& path, base::MessageLoopProxy* cache_thread,
               net::NetLog* net_log);
   // mask can be used to limit the usable size of the hash table, for testing.
   BackendImpl(const FilePath& path, uint32 mask,
               base::MessageLoopProxy* cache_thread, net::NetLog* net_log);
-  ~BackendImpl();
+  virtual ~BackendImpl();
 
   // Returns a new backend with the desired flags. See the declaration of
   // CreateCacheBackend().
   static int CreateBackend(const FilePath& full_path, bool force,
                            int max_bytes, net::CacheType type,
                            uint32 flags, base::MessageLoopProxy* thread,
                            net::NetLog* net_log, Backend** backend,
                            CompletionCallback* callback);
 
   // Performs general initialization for this current instance of the cache.
@@ skipping 318 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(BackendImpl);
 };
 
 // Returns the prefered max cache size given the available disk space.
 NET_TEST int PreferedCacheSize(int64 available);
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_BACKEND_IMPL_H_