Virtual destructors should have virtual keyword.

net/disk_cache/file_lock.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_FILE_LOCK_H__
 #define NET_DISK_CACHE_FILE_LOCK_H__
 #pragma once
 
@@ skipping 13 matching lines @@
 //      header->max_entries = num_entries;
 //      // At this point the destructor is going to release the lock.
 //    }
 // It is important to perform Lock() and Unlock() operations in the right order,
 // because otherwise the desired effect of the "lock" will not be achieved. If
 // the operations are inlined / optimized, the "locked" operations can happen
 // outside the lock.
 class NET_TEST FileLock {
  public:
   explicit FileLock(BlockFileHeader* header);
-  virtual ~FileLock() {
-    Unlock();
-  }
+  virtual ~FileLock();
+
   // Virtual to make sure the compiler never inlines the calls.
   virtual void Lock();
   virtual void Unlock();
  private:
   bool acquired_;
   volatile int32* updating_;
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_FILE_LOCK_H__