Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 3897 matching lines @@
 
 void RenderLayer::updateOrRemoveFilterEffectRenderer()
 {
     // FilterEffectRenderer is only used to render the filters in software mode,
     // so we always need to run updateOrRemoveFilterEffectRenderer after the composited
     // mode might have changed for this layer.
     if (!paintsWithFilters()) {
         // Don't delete the whole filter info here, because we might use it
         // for loading CSS shader files.
         if (RenderLayerFilterInfo* filterInfo = this->filterInfo())
-            filterInfo->setRenderer(0);
+            filterInfo->setRenderer(nullptr);
 
         return;
     }
 
     RenderLayerFilterInfo* filterInfo = ensureFilterInfo();
     if (!filterInfo->renderer()) {
         RefPtr<FilterEffectRenderer> filterRenderer = FilterEffectRenderer::create();
         filterRenderer->setIsAccelerated(renderer()->frame()->settings()->acceleratedFiltersEnabled());
         filterInfo->setRenderer(filterRenderer.release());
 
         // We can optimize away code paths in other places if we know that there are no software filters.
         renderer()->document().view()->setHasSoftwareFilters(true);
     }
 
     // If the filter fails to build, remove it from the layer. It will still attempt to
     // go through regular processing (e.g. compositing), but never apply anything.
     if (!filterInfo->renderer()->build(renderer(), computeFilterOperations(renderer()->style())))
-        filterInfo->setRenderer(0);
+        filterInfo->setRenderer(nullptr);
 }
 
 void RenderLayer::filterNeedsRepaint()
 {
     {
         DeprecatedScheduleStyleRecalcDuringLayout marker(renderer()->document().lifecycle());
         // It's possible for scheduleLayerUpdate to schedule a style recalc, which
         // is a problem because this function can be called while performing layout.
         // Presumably this represents an illegal data flow of layout or compositing
         // information into the style system.
@@ skipping 63 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif