Virtual destructors should have virtual keyword.

net/disk_cache/mem_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_MEM_BACKEND_IMPL_H__
 #define NET_DISK_CACHE_MEM_BACKEND_IMPL_H__
 #pragma once
 
 #include "base/hash_tables.h"
 
 #include "net/disk_cache/disk_cache.h"
 #include "net/disk_cache/mem_rankings.h"
 
 namespace net {
 class NetLog;
 }  // namespace net
 
 namespace disk_cache {
 
 class MemEntryImpl;
 
 // This class implements the Backend interface. An object of this class handles
 // the operations of the cache without writing to disk.
 class NET_TEST MemBackendImpl : public Backend {
  public:
   explicit MemBackendImpl(net::NetLog* net_log);
-  ~MemBackendImpl();
+  virtual ~MemBackendImpl();
 
   // Returns an instance of a Backend implemented only in memory. The returned
   // object should be deleted when not needed anymore. max_bytes is the maximum
   // size the cache can grow to. If zero is passed in as max_bytes, the cache
   // will determine the value to use based on the available memory. The returned
   // pointer can be NULL if a fatal error is found.
   static Backend* CreateBackend(int max_bytes, net::NetLog* net_log);
 
   // Performs general initialization for this current instance of the cache.
   bool Init();
@@ skipping 69 matching lines @@
   int32 current_size_;
 
   net::NetLog* net_log_;
 
   DISALLOW_COPY_AND_ASSIGN(MemBackendImpl);
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_MEM_BACKEND_IMPL_H__