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

Source/core/animation/animatable/AnimatableLengthSize.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 15 matching lines @@
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "core/animation/animatable/AnimatableLengthSize.h"
 
 namespace blink {
 
-PassRefPtrWillBeRawPtr<AnimatableValue> AnimatableLengthSize::interpolateTo(const AnimatableValue* value, double fraction) const
+AnimatableValue* AnimatableLengthSize::interpolateTo(const AnimatableValue* value, double fraction) const
 {
     const AnimatableLengthSize* lengthSize = toAnimatableLengthSize(value);
     return AnimatableLengthSize::create(
         AnimatableValue::interpolate(this->width(), lengthSize->width(), fraction),
         AnimatableValue::interpolate(this->height(), lengthSize->height(), fraction));
 }
 
 bool AnimatableLengthSize::equalTo(const AnimatableValue* value) const
 {
     const AnimatableLengthSize* lengthSize = toAnimatableLengthSize(value);
     return width()->equals(lengthSize->width()) && height()->equals(lengthSize->height());
 }
 
 DEFINE_TRACE(AnimatableLengthSize)
 {
     visitor->trace(m_width);
     visitor->trace(m_height);
     AnimatableValue::trace(visitor);
 }
 
 }