Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/html/shadow/SpinButtonElement.cpp

 /*
  * Copyright (C) 2006, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google 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.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 175 matching lines @@
         m_spinButtonOwner->spinButtonStepUp();
     else if (amount < 0)
         m_spinButtonOwner->spinButtonStepDown();
 }
 
 void SpinButtonElement::releaseCapture()
 {
     stopRepeatingTimer();
     if (m_capturing) {
         if (Frame* frame = document().frame()) {
-            frame->eventHandler().setCapturingMouseEventsNode(0);
+            frame->eventHandler().setCapturingMouseEventsNode(nullptr);
             m_capturing = false;
             if (Page* page = document().page())
                 page->chrome().unregisterPopupOpeningObserver(this);
         }
     }
 }
 
 bool SpinButtonElement::matchesReadOnlyPseudoClass() const
 {
     return shadowHost()->matchesReadOnlyPseudoClass();
@@ skipping 42 matching lines @@
         m_upDownState = Indeterminate;
     HTMLDivElement::setHovered(flag);
 }
 
 bool SpinButtonElement::shouldRespondToMouseEvents()
 {
     return !m_spinButtonOwner || m_spinButtonOwner->shouldSpinButtonRespondToMouseEvents();
 }
 
 }