Use StringKeyframes to make CSS Animations responsive to style changes

Source/core/animation/KeyframeEffectModel.h

Index: Source/core/animation/KeyframeEffectModel.h
diff --git a/Source/core/animation/KeyframeEffectModel.h b/Source/core/animation/KeyframeEffectModel.h
index dd5536f04dab9ad6c9455be7db54885f48579d5c..aa8c02dc7193f8211aa5de38ddc7cfde3441f9ae 100644
--- a/Source/core/animation/KeyframeEffectModel.h
+++ b/Source/core/animation/KeyframeEffectModel.h
@@ -104,7 +104,7 @@ public:
     // FIXME: This is a hack used to resolve CSSValues to AnimatableValues while we have a valid handle on an element.
     // This should be removed once AnimatableValues are obsolete.
     void forceConversionsToAnimatableValues(Element&, const LayoutStyle* baseStyle);
-    void updateNeutralKeyframeAnimatableValues(CSSPropertyID, PassRefPtrWillBeRawPtr<AnimatableValue>);
+    bool updateNeutralKeyframeAnimatableValues(CSSPropertyID, PassRefPtrWillBeRawPtr<AnimatableValue>);
 
     template<typename T>
     inline void forEachInterpolation(const T& callback) { m_interpolationEffect->forEachInterpolation(callback); }