Virtual destructors should have virtual keyword.

net/disk_cache/file_lock.cc

 // 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.
 
 #include "net/disk_cache/file_lock.h"
 
 namespace disk_cache {
 
 FileLock::FileLock(BlockFileHeader* header) {
   updating_ = &header->updating;
   (*updating_)++;
   acquired_ = true;
 }
 
+FileLock::~FileLock() {
+  Unlock();
+}
+
 void FileLock::Lock() {
   if (acquired_)
     return;
   (*updating_)++;
 }
 
 void FileLock::Unlock() {
   if (!acquired_)
     return;
   (*updating_)--;
 }
 
 }  // namespace disk_cache