Virtual destructors should have virtual keyword.

chrome/browser/history/top_sites_backend.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.
 
 #ifndef CHROME_BROWSER_HISTORY_TOP_SITES_BACKEND_H_
 #define CHROME_BROWSER_HISTORY_TOP_SITES_BACKEND_H_
 #pragma once
 
 #include "base/callback_old.h"
 #include "base/file_path.h"
@@ skipping 51 matching lines @@
 
   // Schedules a request that does nothing on the DB thread, but then notifies
   // the callback on the calling thread. This is used to make sure the db has
   // finished processing a request.
   Handle DoEmptyRequest(CancelableRequestConsumerBase* consumer,
                         EmptyRequestCallback* callback);
 
  private:
   friend class base::RefCountedThreadSafe<TopSitesBackend>;
 
-  ~TopSitesBackend();
+  virtual ~TopSitesBackend();
 
   // Invokes Init on the db_.
   void InitDBOnDBThread(const FilePath& path);
 
   // Shuts down the db.
   void ShutdownDBOnDBThread();
 
   // Does the work of getting the most visted thumbnails.
   void GetMostVisitedThumbnailsOnDBThread(
       scoped_refptr<GetMostVisitedThumbnailsRequest> request);
@@ skipping 15 matching lines @@
   FilePath db_path_;
 
   scoped_ptr<TopSitesDatabase> db_;
 
   DISALLOW_COPY_AND_ASSIGN(TopSitesBackend);
 };
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_TOP_SITES_BACKEND_H_