Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/platform/fonts/FontDescription.cpp

 /*
  * Copyright (C) 2007 Nicholas Shanks <contact@nickshanks.com>
  * Copyright (C) 2008 Apple 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.
@@ skipping 125 matching lines @@
     default:
         ASSERT_NOT_REACHED();
     }
     setItalic((traitsMask & FontStyleItalicMask) ? FontItalicOn : FontItalicOff);
     setSmallCaps((traitsMask & FontVariantSmallCapsMask) ? FontSmallCapsOn : FontSmallCapsOff);
 }
 
 FontDescription FontDescription::makeNormalFeatureSettings() const
 {
     FontDescription normalDescription(*this);
-    normalDescription.setFeatureSettings(0);
+    normalDescription.setFeatureSettings(nullptr);
     return normalDescription;
 }
 
 float FontDescription::effectiveFontSize() const
 {
     float size = (RuntimeEnabledFeatures::subpixelFontScalingEnabled())
         ? computedSize()
         : computedPixelSize();
 
     // Ensure that the effective precision matches the font-cache precision.
@@ skipping 63 matching lines @@
         break;
     case FontDescription::EnabledLigaturesState:
         m_typesettingFeatures |= Ligatures;
         break;
     case FontDescription::NormalLigaturesState:
         break;
     }
 }
 
 } // namespace WebCore