Virtual destructors should have virtual keyword.

webkit/support/simple_database_system.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 WEBKIT_SUPPORT_SIMPLE_DATABASE_SYSTEM_H_
 #define WEBKIT_SUPPORT_SIMPLE_DATABASE_SYSTEM_H_
 
 #include "base/file_path.h"
 #include "base/hash_tables.h"
 #include "base/memory/ref_counted.h"
@@ skipping 11 matching lines @@
 class MessageLoopProxy;
 class WaitableEvent;
 }
 
 class SimpleDatabaseSystem : public webkit_database::DatabaseTracker::Observer,
                              public WebKit::WebDatabaseObserver {
  public:
   static SimpleDatabaseSystem* GetInstance();
 
   SimpleDatabaseSystem();
-  ~SimpleDatabaseSystem();
+  virtual ~SimpleDatabaseSystem();
 
   // WebDatabaseObserver implementation, these are called on the script
   // execution context thread on which the database is opened. This may be
   // the main thread or background WebWorker threads.
   virtual void databaseOpened(const WebKit::WebDatabase& database);
   virtual void databaseModified(const WebKit::WebDatabase& database);
   virtual void databaseClosed(const WebKit::WebDatabase& database);
 
   // SQLite VFS related methods, these are called on webcore's
   // background database threads via the WebKitClient impl.
@@ skipping 51 matching lines @@
 
   // Data members to support waiting for all connections to be closed.
   scoped_refptr<webkit_database::DatabaseConnectionsWrapper> open_connections_;
 
   static SimpleDatabaseSystem* instance_;
 };
 
 DISABLE_RUNNABLE_METHOD_REFCOUNT(SimpleDatabaseSystem);
 
 #endif  // WEBKIT_SUPPORT_SIMPLE_DATABASE_SYSTEM_H_