Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/rendering/RenderLayer.cpp

Index: Source/core/rendering/RenderLayer.cpp
diff --git a/Source/core/rendering/RenderLayer.cpp b/Source/core/rendering/RenderLayer.cpp
index 3b4e408284cf6373ce2fe37ab77c5c2d9e20f1b6..c191e8b662615af6d3738fbd839106c6bd78cd9a 100644
--- a/Source/core/rendering/RenderLayer.cpp
+++ b/Source/core/rendering/RenderLayer.cpp
@@ -3915,7 +3915,7 @@ void RenderLayer::updateOrRemoveFilterEffectRenderer()
         // 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;
     }
@@ -3933,7 +3933,7 @@ void RenderLayer::updateOrRemoveFilterEffectRenderer()
     // 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()