Revert of Remove the concept of a cleanup task

Source/modules/webdatabase/DatabaseThread.cpp

 /*
  * Copyright (C) 2007, 2008, 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:
  *
  * 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 53 matching lines @@
 void DatabaseThread::start()
 {
     if (m_thread)
         return;
     m_thread = WebThreadSupportingGC::create("WebCore: Database");
     m_thread->postTask(FROM_HERE, new Task(threadSafeBind(&DatabaseThread::setupDatabaseThread, this)));
 }
 
 void DatabaseThread::setupDatabaseThread()
 {
-    m_thread->initialize();
+    m_thread->attachGC();
 }
 
 void DatabaseThread::terminate()
 {
     TaskSynchronizer sync;
     {
         MutexLocker lock(m_terminationRequestedMutex);
         ASSERT(!m_terminationRequested);
         m_terminationRequested = true;
         m_cleanupSync = &sync;
@@ skipping 30 matching lines @@
         for (HeapHashSet<Member<Database>>::iterator it = openSetCopy.begin(); it != end; ++it)
             (*it)->close();
     }
     m_openDatabaseSet.clear();
 
     m_thread->postTask(FROM_HERE, new Task(WTF::bind(&DatabaseThread::cleanupDatabaseThreadCompleted, this)));
 }
 
 void DatabaseThread::cleanupDatabaseThreadCompleted()
 {
-    m_thread->shutdown();
+    m_thread->detachGC();
     if (m_cleanupSync) // Someone wanted to know when we were done cleaning up.
         m_cleanupSync->taskCompleted();
 }
 
 void DatabaseThread::recordDatabaseOpen(Database* database)
 {
     ASSERT(isDatabaseThread());
     ASSERT(database);
     ASSERT(!m_openDatabaseSet.contains(database));
     MutexLocker lock(m_terminationRequestedMutex);
@@ skipping 19 matching lines @@
 
 void DatabaseThread::scheduleTask(PassOwnPtr<DatabaseTask> task)
 {
     ASSERT(m_thread);
     ASSERT(!terminationRequested());
     // WebThread takes ownership of the task.
     m_thread->postTask(FROM_HERE, new Task(threadSafeBind(&DatabaseTask::run, task)));
 }
 
 } // namespace blink