Web Animations: Refactor KeyframeEffectModel to work via an InterpolationEffect.

Source/core/animation/AnimatableValue.h

 /*
  * 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 45 matching lines @@
     {
         return isSameType(value) && equalTo(value);
     }
     bool equals(const AnimatableValue& value) const
     {
         return equals(&value);
     }
 
     virtual bool dependsOnUnderlyingValue() const OVERRIDE FINAL { return false; }
     virtual PassRefPtr<AnimatableValue> compositeOnto(const AnimatableValue*) const OVERRIDE FINAL { return takeConstRef(this); }
+    virtual bool isAnimatableValue() const { return true; }
 
     bool isClipPathOperation() const { return type() == TypeClipPathOperation; }
     bool isColor() const { return type() == TypeColor; }
     bool isDouble() const { return type() == TypeDouble; }
     bool isFilterOperations() const { return type() == TypeFilterOperations; }
     bool isImage() const { return type() == TypeImage; }
     bool isLength() const { return type() == TypeLength; }
     bool isLengthBox() const { return type() == TypeLengthBox; }
     bool isLengthBoxAndBool() const { return type() == TypeLengthBoxAndBool; }
     bool isLengthPoint() const { return type() == TypeLengthPoint; }
@@ skipping 58 matching lines @@
     virtual bool equalTo(const AnimatableValue*) const = 0;
 
     virtual double distanceTo(const AnimatableValue*) const;
 
     friend class KeyframeEffectModel;
 };
 
 #define DEFINE_ANIMATABLE_VALUE_TYPE_CASTS(thisType, predicate) \
     DEFINE_TYPE_CASTS(thisType, AnimatableValue, value, value->predicate, value.predicate)
 
+DEFINE_TYPE_CASTS(AnimatableValue, AnimationEffect::CompositableValue, value, value->isAnimatableValue(), value.isAnimatableValue());
+
 } // namespace WebCore
 
 #endif // AnimatableValue_h