CSSValue Immediates: Replace CSSValue usage with const references

Source/core/animation/LengthBoxStyleInterpolation.h

Index: Source/core/animation/LengthBoxStyleInterpolation.h
diff --git a/Source/core/animation/LengthBoxStyleInterpolation.h b/Source/core/animation/LengthBoxStyleInterpolation.h
index c7dd881c4eb982171c08388dfbc360932f401b77..0dfa2418dd6dca7a5545aab2f391d6c18bccb236 100644
--- a/Source/core/animation/LengthBoxStyleInterpolation.h
+++ b/Source/core/animation/LengthBoxStyleInterpolation.h
@@ -14,7 +14,7 @@ namespace blink {
 
 class CORE_EXPORT LengthBoxStyleInterpolation : public StyleInterpolation {
 public:
-    static PassRefPtrWillBeRawPtr<LengthBoxStyleInterpolation> maybeCreateFrom(CSSValue&, CSSValue&, CSSPropertyID);
+    static PassRefPtrWillBeRawPtr<LengthBoxStyleInterpolation> maybeCreateFrom(const CSSValue&, const CSSValue&, CSSPropertyID);
 
     static bool usesDefaultInterpolation(const CSSValue&, const CSSValue&);
 
@@ -22,7 +22,7 @@ public:
     DECLARE_VIRTUAL_TRACE();
 
 private:
-    LengthBoxStyleInterpolation(PassOwnPtrWillBeRawPtr<InterpolableValue> startInterpolation, PassOwnPtrWillBeRawPtr<InterpolableValue> endInterpolation, CSSPropertyID id, CSSValue startCSS, CSSValue endCSS)
+    LengthBoxStyleInterpolation(PassOwnPtrWillBeRawPtr<InterpolableValue> startInterpolation, PassOwnPtrWillBeRawPtr<InterpolableValue> endInterpolation, CSSPropertyID id, const CSSValue& startCSS, const CSSValue& endCSS)
         : StyleInterpolation(startInterpolation, endInterpolation, id)
         , m_startCSSValue(startCSS)
         , m_endCSSValue(endCSS)