Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/workers/Worker.cpp

Index: Source/core/workers/Worker.cpp
diff --git a/Source/core/workers/Worker.cpp b/Source/core/workers/Worker.cpp
index 6fdc15ba89032c564df047ed899cb27a5bbae79a..48dd9013eb68f03969316de5511ee9fe9668aa7b 100644
--- a/Source/core/workers/Worker.cpp
+++ b/Source/core/workers/Worker.cpp
@@ -65,7 +65,7 @@ PassRefPtr<Worker> Worker::create(ExecutionContext* context, const String& url,
 
     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());