[wip] interpolable value refactor. NOT FOR LANDING.

Source/core/animation/AnimatableValue.h

Index: Source/core/animation/AnimatableValue.h
diff --git a/Source/core/animation/AnimatableValue.h b/Source/core/animation/AnimatableValue.h
index 7a46e1fc23a745aa891e3ab21a3009561ffac505..1a954fbfb9a6add42d55162a31707c43cd4852ba 100644
--- a/Source/core/animation/AnimatableValue.h
+++ b/Source/core/animation/AnimatableValue.h
@@ -31,12 +31,13 @@
 #ifndef AnimatableValue_h
 #define AnimatableValue_h
 
+#include "core/animation/AnimationEffect.h"
 #include "core/css/CSSValue.h"
 #include "wtf/RefCounted.h"
 
 namespace WebCore {
 
-class AnimatableValue : public RefCounted<AnimatableValue> {
+class AnimatableValue : public AnimationEffect::CompositableValue {
 public:
     virtual ~AnimatableValue() { }
 
@@ -59,6 +60,10 @@ public:
         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; }
@@ -127,11 +132,15 @@ private:
     virtual AnimatableType type() const = 0;
     // Implementations can assume that the object being compared has the same type as the object this is called on
     virtual bool equalTo(const AnimatableValue*) const = 0;
+
+    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