Add foundation for removing AnimatableValues from StyleInterpolation

Source/core/animation/Interpolation.h

Index: Source/core/animation/Interpolation.h
diff --git a/Source/core/animation/Interpolation.h b/Source/core/animation/Interpolation.h
index c3c62cd9219b4dada27cc4aa122ca627a45856de..57bc190de611f45c5b67115518efb85ec19ade23 100644
--- a/Source/core/animation/Interpolation.h
+++ b/Source/core/animation/Interpolation.h
@@ -17,9 +17,10 @@ class CORE_EXPORT Interpolation : public RefCountedWillBeGarbageCollectedFinaliz
 public:
     virtual ~Interpolation();
 
-    void interpolate(int iteration, double fraction) const;
+    virtual void interpolate(int iteration, double fraction);
 
     virtual bool isStyleInterpolation() const { return false; }
+    virtual bool isInvalidatableStyleInterpolation() const { return false; }
     virtual bool isLegacyStyleInterpolation() const { return false; }
     virtual bool isSVGInterpolation() const { return false; }