Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/animation/KeyframeEffectModel.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 316 matching lines @@
             allOffsetsEqual = false;
             break;
         }
     }
     if (!allOffsetsEqual)
         return;
 
     if (!offset)
         appendKeyframe(m_keyframes.first()->cloneWithOffset(1.0));
     else
-        m_keyframes.insert(0, adoptPtr(new PropertySpecificKeyframe(0.0, 0, AnimatableValue::neutralValue(), CompositeAdd)));
+        m_keyframes.insert(0, adoptPtr(new PropertySpecificKeyframe(0.0, nullptr, AnimatableValue::neutralValue(), CompositeAdd)));
 }
 
 PassRefPtr<AnimationEffect::CompositableValue> KeyframeEffectModel::PropertySpecificKeyframeGroup::sample(int iteration, double offset) const
 {
     // FIXME: Implement accumulation.
     ASSERT_UNUSED(iteration, iteration >= 0);
     ASSERT(!isNull(offset));
 
     // Bail if offset is null, as this can lead to buffer overflow below.
     if (isNull(offset))
@@ skipping 35 matching lines @@
     if ((*after)->offset() == offset)
         return const_cast<CompositableValue*>((*after)->value());
 
     double fraction = (offset - (*before)->offset()) / ((*after)->offset() - (*before)->offset());
     if (const TimingFunction* timingFunction = (*before)->easing())
         fraction = timingFunction->evaluate(fraction, accuracyForKeyframeEasing);
     return BlendedCompositableValue::create((*before)->value(), (*after)->value(), fraction);
 }
 
 } // namespace