Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/clipboard/DataTransferItemList.cpp

 /*
  * Copyright (C) 2006, 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2008, 2009 Google Inc.
  *
  * 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 36 matching lines @@
 size_t DataTransferItemList::length() const
 {
     if (!m_clipboard->canReadTypes())
         return 0;
     return m_dataObject->length();
 }
 
 PassRefPtr<DataTransferItem> DataTransferItemList::item(unsigned long index)
 {
     if (!m_clipboard->canReadTypes())
-        return 0;
+        return nullptr;
     RefPtr<DataObjectItem> item = m_dataObject->item(index);
     if (!item)
-        return 0;
+        return nullptr;
 
     return DataTransferItem::create(m_clipboard, item);
 }
 
 void DataTransferItemList::deleteItem(unsigned long index, ExceptionState& exceptionState)
 {
     if (!m_clipboard->canWriteData()) {
         exceptionState.throwDOMException(InvalidStateError, "The list is not writable.");
         return;
     }
     m_dataObject->deleteItem(index);
 }
 
 void DataTransferItemList::clear()
 {
     if (!m_clipboard->canWriteData())
         return;
     m_dataObject->clearAll();
 }
 
 PassRefPtr<DataTransferItem> DataTransferItemList::add(const String& data, const String& type, ExceptionState& exceptionState)
 {
     if (!m_clipboard->canWriteData())
-        return 0;
+        return nullptr;
     RefPtr<DataObjectItem> item = m_dataObject->add(data, type);
     if (!item) {
         exceptionState.throwDOMException(NotSupportedError, "An item already exists for type '" + type + "'.");
-        return 0;
+        return nullptr;
     }
     return DataTransferItem::create(m_clipboard, item);
 }
 
 PassRefPtr<DataTransferItem> DataTransferItemList::add(PassRefPtr<File> file)
 {
     if (!m_clipboard->canWriteData())
-        return 0;
+        return nullptr;
     RefPtr<DataObjectItem> item = m_dataObject->add(file);
     if (!item)
-        return 0;
+        return nullptr;
     return DataTransferItem::create(m_clipboard, item);
 }
 
 DataTransferItemList::DataTransferItemList(PassRefPtr<Clipboard> clipboard, PassRefPtr<DataObject> dataObject)
     : m_clipboard(clipboard)
     , m_dataObject(dataObject)
 {
     ScriptWrappable::init(this);
 }
 
 } // namespace WebCore