Support per property CSS Animation stacks

Source/core/animation/css/CSSAnimations.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 111 matching lines @@
     };
 
     using AnimationMap = HeapHashMap<AtomicString, Member<RunningAnimation>>;
     AnimationMap m_animations;
 
     using TransitionMap = HeapHashMap<CSSPropertyID, RunningTransition>;
     TransitionMap m_transitions;
 
     CSSAnimationUpdate m_pendingUpdate;
 
-    ActiveInterpolationMap m_previousActiveInterpolationsForAnimations;
+    ActiveInterpolationsMap m_previousActiveInterpolationsForAnimations;
 
     static void calculateAnimationUpdate(CSSAnimationUpdate&, const Element* animatingElement, Element&, const ComputedStyle&, ComputedStyle* parentStyle, StyleResolver*);
     static void calculateTransitionUpdate(CSSAnimationUpdate&, const Element* animatingElement, const ComputedStyle&);
     static void calculateTransitionUpdateForProperty(CSSPropertyID, const CSSTransitionData&, size_t transitionIndex, const ComputedStyle& oldStyle, const ComputedStyle&, const TransitionMap* activeTransitions, CSSAnimationUpdate&, const Element*);
 
     static void calculateAnimationActiveInterpolations(CSSAnimationUpdate&, const Element* animatingElement, double timelineCurrentTime);
     static void calculateTransitionActiveInterpolations(CSSAnimationUpdate&, const Element* animatingElement, double timelineCurrentTime);
 
     class AnimationEventDelegate final : public AnimationEffect::EventDelegate {
     public:
@@ skipping 40 matching lines @@
 
         RawPtrWillBeMember<Element> m_transitionTarget;
         const CSSPropertyID m_property;
         AnimationEffect::Phase m_previousPhase;
     };
 };
 
 } // namespace blink
 
 #endif