[Oilpan] Migrate most classes under core/animations to Oilpan heap.

Source/core/animation/animatable/AnimatableLength.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 49 matching lines @@
 
 Length AnimatableLength::length(float zoom, ValueRange range) const
 {
     if (!m_hasPercent)
         return Length(clampNumber(m_pixels, range) * zoom, Fixed);
     if (!m_hasPixels)
         return Length(clampNumber(m_percent, range), Percent);
     return Length(CalculationValue::create(PixelsAndPercent(m_pixels * zoom, m_percent), range));
 }
 
-PassRefPtrWillBeRawPtr<AnimatableValue> AnimatableLength::interpolateTo(const AnimatableValue* value, double fraction) const
+AnimatableValue* AnimatableLength::interpolateTo(const AnimatableValue* value, double fraction) const
 {
     const AnimatableLength* length = toAnimatableLength(value);
     return create(blend(m_pixels, length->m_pixels, fraction), blend(m_percent, length->m_percent, fraction),
         m_hasPixels || length->m_hasPixels, m_hasPercent || length->m_hasPercent);
 }
 
 bool AnimatableLength::equalTo(const AnimatableValue* value) const
 {
     const AnimatableLength* length = toAnimatableLength(value);
     return m_pixels == length->m_pixels && m_percent == length->m_percent && m_hasPixels == length->m_hasPixels && m_hasPercent == length->m_hasPercent;
 }
 
 } // namespace blink