Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/css/resolver/AnimatedStyleBuilder.cpp

 /*
  * Copyright (C) 2013 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 159 matching lines @@
             prev->setNext(fillLayer);
         }
         const AnimatableValue* layerValue = values[i].get();
         switch (property) {
         case CSSPropertyBackgroundImage:
         case CSSPropertyWebkitMaskImage:
             if (layerValue->isImage()) {
                 fillLayer->setImage(toAnimatableImage(layerValue)->toStyleImage());
             } else {
                 ASSERT(toAnimatableUnknown(layerValue)->toCSSValueID() == CSSValueNone);
-                fillLayer->setImage(0);
+                fillLayer->setImage(nullptr);
             }
             break;
         case CSSPropertyBackgroundPositionX:
         case CSSPropertyWebkitMaskPositionX:
             fillLayer->setXPosition(animatableValueToLength(layerValue, state));
             break;
         case CSSPropertyBackgroundPositionY:
         case CSSPropertyWebkitMaskPositionY:
             fillLayer->setYPosition(animatableValueToLength(layerValue, state));
             break;
@@ skipping 397 matching lines @@
         return;
     case CSSPropertyZoom:
         style->setZoom(clampTo<float>(toAnimatableDouble(value)->toDouble(), std::numeric_limits<float>::denorm_min()));
         return;
     default:
         ASSERT_NOT_REACHED();
     }
 }
 
 } // namespace WebCore