Rollback transactions by observing them weakly from DatabaseSync.

Source/modules/webdatabase/SQLTransactionBackendSync.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 32 matching lines @@
 
 class DatabaseSync;
 class SQLResultSet;
 class SQLTransactionClient;
 class SQLTransactionSyncCallback;
 class SQLValue;
 class SQLiteTransaction;
 class ExceptionState;
 
 // Instances of this class should be created and used only on the worker's context thread.
-class SQLTransactionBackendSync : public RefCounted<SQLTransactionBackendSync> {
+class SQLTransactionBackendSync : public RefCountedWillBeGarbageCollectedFinalized<SQLTransactionBackendSync> {
 public:
     ~SQLTransactionBackendSync();
+    void trace(Visitor*);
 
     PassRefPtr<SQLResultSet> executeSQL(const String& sqlStatement, const Vector<SQLValue>& arguments, ExceptionState&);
 
     DatabaseSync* database() { return m_database.get(); }
 
     void begin(ExceptionState&);
     void execute(ExceptionState&);
     void commit(ExceptionState&);
     void rollback();
+    void rollbackIfInProgress();
 
 private:
     SQLTransactionBackendSync(DatabaseSync*, PassOwnPtr<SQLTransactionSyncCallback>, bool readOnly);
 
-    RefPtrWillBePersistent<DatabaseSync> m_database;
+    RefPtrWillBeMember<DatabaseSync> m_database;
     OwnPtr<SQLTransactionSyncCallback> m_callback;
     bool m_readOnly;
     bool m_hasVersionMismatch;
 
     bool m_modifiedDatabase;
     OwnPtr<SQLTransactionClient> m_transactionClient;
     OwnPtr<SQLiteTransaction> m_sqliteTransaction;
 
     friend class SQLTransactionSync; // FIXME: Remove this once the front-end has been properly isolated.
 };
 
 } // namespace WebCore
 
 #endif // SQLTransactionBackendSync_h