Web Animations: define distance for AnimatableColor

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 28 matching lines @@
 
 class AnimatableValue : public AnimationEffect::CompositableValue {
 public:
     virtual ~AnimatableValue() { }
 
     static const AnimatableValue* neutralValue();
 
     static PassRefPtr<AnimatableValue> interpolate(const AnimatableValue*, const AnimatableValue*, double fraction);
     // For noncommutative values read add(A, B) to mean the value A with B composed onto it.
     static PassRefPtr<AnimatableValue> add(const AnimatableValue*, const AnimatableValue*);
+    static double distance(const AnimatableValue* from, const AnimatableValue* to);
     static bool usesDefaultInterpolation(const AnimatableValue* from, const AnimatableValue* to)
     {
         return !from->isSameType(to) || from->usesDefaultInterpolationWith(to);
     }
 
     bool equals(const AnimatableValue* value) const
     {
         return isSameType(value) && equalTo(value);
     }
     bool equals(const AnimatableValue& value) const
@@ skipping 66 matching lines @@
 
 
     template <class T>
     static PassRefPtr<T> takeConstRef(const T* value) { return PassRefPtr<T>(const_cast<T*>(value)); }
 
 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;
 
+    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)
 
 } // namespace WebCore
 
 #endif // AnimatableValue_h