Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/web/PopupListBox.cpp

 /*
  * Copyright (c) 2011, 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 111 matching lines @@
         return false;
 
     selectIndex(pointToRowIndex(event.position()));
     return true;
 }
 
 bool PopupListBox::handleMouseReleaseEvent(const PlatformMouseEvent& event)
 {
     if (m_capturingScrollbar) {
         m_capturingScrollbar->mouseUp(event);
-        m_capturingScrollbar = 0;
+        m_capturingScrollbar = nullptr;
         return true;
     }
 
     if (!isPointInBounds(event.position()))
         return true;
 
     if (acceptIndex(pointToRowIndex(event.position())) && m_focusedElement) {
         m_focusedElement->dispatchMouseEvent(event, EventTypeNames::mouseup);
         m_focusedElement->dispatchMouseEvent(event, EventTypeNames::click);
 
         // Clear m_focusedElement here, because we cannot clear in hidePopup()
         // which is called before dispatchMouseEvent() is called.
-        m_focusedElement = 0;
+        m_focusedElement = nullptr;
     }
 
     return true;
 }
 
 bool PopupListBox::handleWheelEvent(const PlatformWheelEvent& event)
 {
     if (!isPointInBounds(event.position())) {
         abandon();
         return true;
@@ skipping 309 matching lines @@
 }
 
 Font PopupListBox::getRowFont(int rowIndex)
 {
     Font itemFont = m_popupClient->itemStyle(rowIndex).font();
     if (m_popupClient->itemIsLabel(rowIndex)) {
         // Bold-ify labels (ie, an <optgroup> heading).
         FontDescription d = itemFont.fontDescription();
         d.setWeight(FontWeightBold);
         Font font(d);
-        font.update(0);
+        font.update(nullptr);
         return font;
     }
 
     return itemFont;
 }
 
 void PopupListBox::abandon()
 {
     RefPtr<PopupListBox> keepAlive(this);
 
@@ skipping 332 matching lines @@
 {
     return numItems() && IntRect(0, 0, width(), height()).contains(point);
 }
 
 int PopupListBox::popupContentHeight() const
 {
     return height();
 }
 
 } // namespace blink