Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/rendering/RenderScrollbar.cpp

 /*
  * Copyright (C) 2008, 2009 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 130 matching lines @@
     updateScrollbarPart(oldPart);
     updateScrollbarPart(part);
 
     updateScrollbarPart(ScrollbarBGPart);
     updateScrollbarPart(TrackBGPart);
 }
 
 PassRefPtr<RenderStyle> RenderScrollbar::getScrollbarPseudoStyle(ScrollbarPart partType, PseudoId pseudoId)
 {
     if (!owningRenderer())
-        return 0;
+        return nullptr;
 
     RefPtr<RenderStyle> result = owningRenderer()->getUncachedPseudoStyle(PseudoStyleRequest(pseudoId, this, partType), owningRenderer()->style());
     // Scrollbars for root frames should always have background color
     // unless explicitly specified as transparent. So we force it.
     // This is because WebKit assumes scrollbar to be always painted and missing background
     // causes visual artifact like non-repainted dirty region.
     if (result && m_owningFrame && m_owningFrame->view() && !m_owningFrame->view()->isTransparent() && !result->hasBackground())
         result->setBackgroundColor(StyleColor(Color::white));
 
     return result;
@@ skipping 54 matching lines @@
     }
     ASSERT_NOT_REACHED();
     return SCROLLBAR;
 }
 
 void RenderScrollbar::updateScrollbarPart(ScrollbarPart partType, bool destroy)
 {
     if (partType == NoPart)
         return;
 
-    RefPtr<RenderStyle> partStyle = !destroy ? getScrollbarPseudoStyle(partType,  pseudoForScrollbarPart(partType)) : PassRefPtr<RenderStyle>(0);
+    RefPtr<RenderStyle> partStyle = !destroy ? getScrollbarPseudoStyle(partType,  pseudoForScrollbarPart(partType)) : PassRefPtr<RenderStyle>(nullptr);
 
     bool needRenderer = !destroy && partStyle && partStyle->display() != NONE && partStyle->visibility() == VISIBLE;
 
     if (needRenderer && partStyle->display() != BLOCK) {
         // See if we are a button that should not be visible according to OS settings.
         ScrollbarButtonsPlacement buttonsPlacement = theme()->buttonsPlacement();
         switch (partType) {
             case BackButtonStartPart:
                 needRenderer = (buttonsPlacement == ScrollbarButtonsSingle || buttonsPlacement == ScrollbarButtonsDoubleStart ||
                                 buttonsPlacement == ScrollbarButtonsDoubleBoth);
@@ skipping 113 matching lines @@
 int RenderScrollbar::minimumThumbLength()
 {
     RenderScrollbarPart* partRenderer = m_parts.get(ThumbPart);
     if (!partRenderer)
         return 0;
     partRenderer->layout();
     return orientation() == HorizontalScrollbar ? partRenderer->width() : partRenderer->height();
 }
 
 }