Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/workers/Worker.cpp

 /*
  * Copyright (C) 2008, 2010 Apple Inc. All Rights Reserved.
  * Copyright (C) 2009 Google 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 47 matching lines @@
     ASSERT(document->page());
     WorkerGlobalScopeProxyProvider* proxyProvider = WorkerGlobalScopeProxyProvider::from(*document->page());
     ASSERT(proxyProvider);
 
     RefPtr<Worker> worker = adoptRef(new Worker(context));
 
     worker->suspendIfNeeded();
 
     KURL scriptURL = worker->resolveURL(url, exceptionState);
     if (scriptURL.isEmpty())
-        return 0;
+        return nullptr;
 
     // The worker context does not exist while loading, so we must ensure that the worker object is not collected, nor are its event listeners.
     worker->setPendingActivity(worker.get());
 
     worker->m_scriptLoader = WorkerScriptLoader::create();
     worker->m_scriptLoader->loadAsynchronously(context, scriptURL, DenyCrossOriginRequests, worker.get());
     worker->m_contextProxy = proxyProvider->createWorkerGlobalScopeProxy(worker.get());
     return worker.release();
 }
 
@@ skipping 49 matching lines @@
             startMode = PauseWorkerGlobalScopeOnStart;
         m_contextProxy->startWorkerGlobalScope(m_scriptLoader->url(), executionContext()->userAgent(m_scriptLoader->url()), m_scriptLoader->script(), startMode);
         InspectorInstrumentation::scriptImported(executionContext(), m_scriptLoader->identifier(), m_scriptLoader->script());
     }
     m_scriptLoader = nullptr;
 
     unsetPendingActivity(this);
 }
 
 } // namespace WebCore