DatabaseBackend objects should be destructed in the originator thread

Source/modules/webdatabase/DatabaseThread.h

 /*
  * Copyright (C) 2007, 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 43 matching lines @@
     ~DatabaseThread();
 
     void start();
     void requestTermination(DatabaseTaskSynchronizer* cleanupSync);
     bool terminationRequested(DatabaseTaskSynchronizer* taskSynchronizer = 0) const;
 
     void scheduleTask(PassOwnPtr<DatabaseTask>);
 
     void recordDatabaseOpen(DatabaseBackend*);
     void recordDatabaseClosed(DatabaseBackend*);
-    bool isDatabaseOpen(DatabaseBackend*);
 
     bool isDatabaseThread() { return m_thread && m_thread->isCurrentThread(); }
 
     SQLTransactionClient* transactionClient() { return m_transactionClient.get(); }
     SQLTransactionCoordinator* transactionCoordinator() { return m_transactionCoordinator.get(); }
 
 private:
     DatabaseThread();
 
     void cleanupDatabaseThread();
 
     OwnPtr<blink::WebThread> m_thread;
 
     // This set keeps track of the open databases that have been used on this thread.
     typedef HashSet<RefPtr<DatabaseBackend> > DatabaseSet;
     DatabaseSet m_openDatabaseSet;
 
     OwnPtr<SQLTransactionClient> m_transactionClient;
     OwnPtr<SQLTransactionCoordinator> m_transactionCoordinator;
     DatabaseTaskSynchronizer* m_cleanupSync;
 
     mutable Mutex m_terminationRequestedMutex;
     bool m_terminationRequested;
 };
 
 } // namespace WebCore
 
 #endif // DatabaseThread_h