Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/css/CSSFontSelector.cpp

Index: Source/core/css/CSSFontSelector.cpp
diff --git a/Source/core/css/CSSFontSelector.cpp b/Source/core/css/CSSFontSelector.cpp
index 47ee0371d47a9350d86b9af91eda2e84b46962c8..90f1df5c24302fb0b75210b3a65acf33adbc043d 100644
--- a/Source/core/css/CSSFontSelector.cpp
+++ b/Source/core/css/CSSFontSelector.cpp
@@ -188,7 +188,7 @@ PassRefPtr<FontData> CSSFontSelector::getFontData(const FontDescription& fontDes
     // Try to return the correct font based off our settings, in case we were handed the generic font family name.
     AtomicString settingsFamilyName = familyNameFromSettings(m_genericFontFamilySettings, fontDescription, familyName);
     if (settingsFamilyName.isEmpty())
-        return 0;
+        return nullptr;
 
     return FontCache::fontCache()->getFontData(fontDescription, settingsFamilyName);
 }