Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/loader/HistoryItem.cpp

Index: Source/core/loader/HistoryItem.cpp
diff --git a/Source/core/loader/HistoryItem.cpp b/Source/core/loader/HistoryItem.cpp
index e9600e923d935a4b03d6ebae2a109b103e38e7ac..6cd6cdadaaab11003bb5148831cf1a9582de4a6c 100644
--- a/Source/core/loader/HistoryItem.cpp
+++ b/Source/core/loader/HistoryItem.cpp
@@ -221,7 +221,7 @@ void HistoryItem::setFormInfoFromRequest(const ResourceRequest& request)
         m_formData = request.httpBody();
         m_formContentType = request.httpContentType();
     } else {
-        m_formData = 0;
+        m_formData = nullptr;
         m_formContentType = nullAtom;
     }
 }