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

Source/core/animation/LengthInterpolationType.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef LengthInterpolationType_h
 #define LengthInterpolationType_h
 
 #include "core/animation/InterpolationType.h"
 #include "core/animation/LengthPropertyFunctions.h"
 
 namespace blink {
 
 class LengthInterpolationType : public InterpolationType {
 public:
     LengthInterpolationType(CSSPropertyID);
 
-    PassOwnPtrWillBeRawPtr<InterpolationValue> maybeConvertUnderlyingValue(const StyleResolverState&) const final;
+    InterpolationValue* maybeConvertUnderlyingValue(const StyleResolverState&) const final;
     void apply(const InterpolableValue&, const NonInterpolableValue*, StyleResolverState&) const final;
 
 private:
-    PassOwnPtrWillBeRawPtr<InterpolationValue> maybeConvertLength(const Length&, float zoom) const;
-    PassOwnPtrWillBeRawPtr<InterpolationValue> maybeConvertNeutral() const final;
-    PassOwnPtrWillBeRawPtr<InterpolationValue> maybeConvertInitial() const final;
-    PassOwnPtrWillBeRawPtr<InterpolationValue> maybeConvertInherit(const StyleResolverState*, ConversionCheckers&) const final;
-    PassOwnPtrWillBeRawPtr<InterpolationValue> maybeConvertValue(const CSSValue&, const StyleResolverState*, ConversionCheckers&) const final;
+    InterpolationValue* maybeConvertLength(const Length&, float zoom) const;
+    InterpolationValue* maybeConvertNeutral() const final;
+    InterpolationValue* maybeConvertInitial() const final;
+    InterpolationValue* maybeConvertInherit(const StyleResolverState*, ConversionCheckers&) const final;
+    InterpolationValue* maybeConvertValue(const CSSValue&, const StyleResolverState*, ConversionCheckers&) const final;
 
     const ValueRange m_valueRange;
 };
 
 } // namespace blink
 
 #endif // LengthInterpolationType_h