CSSValue Immediates: Replace CSSPrimitiveValue usage with const references

Source/core/animation/StringKeyframe.h

Index: Source/core/animation/StringKeyframe.h
diff --git a/Source/core/animation/StringKeyframe.h b/Source/core/animation/StringKeyframe.h
index 95b5dc142c5af278d88d42e1adc4ac77124516b1..6c21e8f820f2c72baef3bd550a9998db7a58f0de 100644
--- a/Source/core/animation/StringKeyframe.h
+++ b/Source/core/animation/StringKeyframe.h
@@ -41,9 +41,9 @@ public:
 
     class CSSPropertySpecificKeyframe : public Keyframe::PropertySpecificKeyframe {
     public:
-        CSSPropertySpecificKeyframe(double offset, PassRefPtr<TimingFunction> easing, NullableCSSValue, EffectModel::CompositeOperation);
+        CSSPropertySpecificKeyframe(double offset, PassRefPtr<TimingFunction> easing, const NullableCSSValue&, EffectModel::CompositeOperation);
 
-        NullableCSSValue value() const { return m_value; }
+        const NullableCSSValue& value() const { return m_value; }
 
         virtual void populateAnimatableValue(CSSPropertyID, Element&, const ComputedStyle* baseStyle) const;
         virtual const PassRefPtrWillBeRawPtr<AnimatableValue> getAnimatableValue() const override final { return m_animatableValueCache.get(); }
@@ -55,14 +55,14 @@ public:
         DECLARE_VIRTUAL_TRACE();
 
     private:
-        CSSPropertySpecificKeyframe(double offset, PassRefPtr<TimingFunction> easing, NullableCSSValue);
+        CSSPropertySpecificKeyframe(double offset, PassRefPtr<TimingFunction> easing, const NullableCSSValue&);
 
         virtual PassOwnPtrWillBeRawPtr<Keyframe::PropertySpecificKeyframe> cloneWithOffset(double offset) const;
         virtual bool isCSSPropertySpecificKeyframe() const override { return true; }
 
-        static bool createInterpolationsFromCSSValues(CSSPropertyID, CSSValue fromCSSValue, CSSValue toCSSValue, Element*, OwnPtrWillBeRawPtr<WillBeHeapVector<RefPtrWillBeMember<Interpolation>>>& interpolations);
+        static bool createInterpolationsFromCSSValues(CSSPropertyID, const CSSValue& fromCSSValue, const CSSValue& toCSSValue, Element*, OwnPtrWillBeRawPtr<WillBeHeapVector<RefPtrWillBeMember<Interpolation>>>& interpolations);
 
-        void populateAnimatableValueCaches(CSSPropertyID, Keyframe::PropertySpecificKeyframe&, Element*, CSSValue& fromCSSValue, CSSValue& toCSSValue) const;
+        void populateAnimatableValueCaches(CSSPropertyID, Keyframe::PropertySpecificKeyframe&, Element*, const CSSValue& fromCSSValue, const CSSValue& toCSSValue) const;
 
         NullableCSSValue m_value;
         mutable RefPtrWillBeMember<AnimatableValue> m_animatableValueCache;