[Reland] Web Animations: Introduce String based KeyframeEffectModel

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 118 matching lines @@
     template <class T>
     static PassRefPtrWillBeRawPtr<T> takeConstRef(const T* value) { return PassRefPtrWillBeRawPtr<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;
+    template <class Keyframe> 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