Add foundation for removing AnimatableValues from StyleInterpolation

Source/core/animation/Keyframe.h

Index: Source/core/animation/Keyframe.h
diff --git a/Source/core/animation/Keyframe.h b/Source/core/animation/Keyframe.h
index 346a10d9971f9f434845aa22640fd9301c732da2..d727efe2a5885bd415b0851a1f6d11d491684dea 100644
--- a/Source/core/animation/Keyframe.h
+++ b/Source/core/animation/Keyframe.h
@@ -52,13 +52,13 @@ public:
 
     DEFINE_INLINE_VIRTUAL_TRACE() { }
 
-    class PropertySpecificKeyframe : public NoBaseWillBeGarbageCollectedFinalized<PropertySpecificKeyframe> {
+    class PropertySpecificKeyframe : public RefCountedWillBeGarbageCollectedFinalized<PropertySpecificKeyframe> {
     public:
         virtual ~PropertySpecificKeyframe() { }
         double offset() const { return m_offset; }
         TimingFunction& easing() const { return *m_easing; }
         EffectModel::CompositeOperation composite() const { return m_composite; }
-        virtual PassOwnPtrWillBeRawPtr<PropertySpecificKeyframe> cloneWithOffset(double offset) const = 0;
+        virtual PassRefPtrWillBeRawPtr<PropertySpecificKeyframe> cloneWithOffset(double offset) const = 0;
 
         // FIXME: Remove this once CompositorAnimations no longer depends on AnimatableValues
         virtual void populateAnimatableValue(CSSPropertyID, Element&, const ComputedStyle* baseStyle) const { }
@@ -68,8 +68,8 @@ public:
         virtual bool isCSSPropertySpecificKeyframe() const { return false; }
         virtual bool isSVGPropertySpecificKeyframe() const { return false; }
 
-        virtual PassOwnPtrWillBeRawPtr<PropertySpecificKeyframe> neutralKeyframe(double offset, PassRefPtr<TimingFunction> easing) const = 0;
-        virtual PassRefPtrWillBeRawPtr<Interpolation> maybeCreateInterpolation(PropertyHandle, Keyframe::PropertySpecificKeyframe& end, Element*, const ComputedStyle* baseStyle) const = 0;
+        virtual PassRefPtrWillBeRawPtr<PropertySpecificKeyframe> neutralKeyframe(double offset, PassRefPtr<TimingFunction> easing) const = 0;
+        virtual PassRefPtrWillBeRawPtr<Interpolation> maybeCreateInterpolation(PropertyHandle, Keyframe::PropertySpecificKeyframe& end, Element*, const ComputedStyle* baseStyle) = 0;
 
         DEFINE_INLINE_VIRTUAL_TRACE() { }
 
@@ -81,7 +81,7 @@ public:
         EffectModel::CompositeOperation m_composite;
     };
 
-    virtual PassOwnPtrWillBeRawPtr<PropertySpecificKeyframe> createPropertySpecificKeyframe(PropertyHandle) const = 0;
+    virtual PassRefPtrWillBeRawPtr<PropertySpecificKeyframe> createPropertySpecificKeyframe(PropertyHandle) const = 0;
 
 protected:
     Keyframe()