Oilpan: DatabaseThread::m_thread should not get destructed during sweeping

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 40 matching lines @@
 class SQLTransactionCoordinator;
 class TaskSynchronizer;
 
 class DatabaseThread : public ThreadSafeRefCountedWillBeGarbageCollectedFinalized<DatabaseThread> {
 public:
     static PassRefPtrWillBeRawPtr<DatabaseThread> create() { return adoptRefWillBeNoop(new DatabaseThread); }
     ~DatabaseThread();
     void trace(Visitor*);
 
     void start();
-    void requestTermination(TaskSynchronizer* cleanupSync);
+    void terminate();
     bool terminationRequested(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 setupDatabaseThread();
     void cleanupDatabaseThread();
     void cleanupDatabaseThreadCompleted();
 
     OwnPtr<WebThreadSupportingGC> m_thread;
 
     // This set keeps track of the open databases that have been used on this thread.
     // This must be updated in the database thread though it is constructed and
     // destructed in the context thread.
     WillBeHeapHashSet<RefPtrWillBeMember<DatabaseBackend> > m_openDatabaseSet;
 
     OwnPtr<SQLTransactionClient> m_transactionClient;
     OwnPtrWillBeMember<SQLTransactionCoordinator> m_transactionCoordinator;
-    TaskSynchronizer* m_cleanupSync;
 
     mutable Mutex m_terminationRequestedMutex;
     bool m_terminationRequested;
 };
 
 } // namespace blink
 
 #endif // DatabaseThread_h