CSSValue Immediates: Replace CSSValue usage with const references

Source/core/animation/LengthBoxStyleInterpolation.cpp

Index: Source/core/animation/LengthBoxStyleInterpolation.cpp
diff --git a/Source/core/animation/LengthBoxStyleInterpolation.cpp b/Source/core/animation/LengthBoxStyleInterpolation.cpp
index 42cda4ba4510bbe4467c30a551c14f78e84a592f..fd57eca852e449830bbf6236c8dae0225d37fe50 100644
--- a/Source/core/animation/LengthBoxStyleInterpolation.cpp
+++ b/Source/core/animation/LengthBoxStyleInterpolation.cpp
@@ -21,7 +21,7 @@ bool onlyInterpolateBetweenLengthAndCSSValueAuto(Rect& startRect, Rect& endRect)
 
 } // namespace
 
-PassRefPtrWillBeRawPtr<LengthBoxStyleInterpolation> LengthBoxStyleInterpolation::maybeCreateFrom(CSSValue& start, CSSValue& end, CSSPropertyID id)
+PassRefPtrWillBeRawPtr<LengthBoxStyleInterpolation> LengthBoxStyleInterpolation::maybeCreateFrom(const CSSValue& start, const CSSValue& end, CSSPropertyID id)
 {
     bool startRect = start.isPrimitiveValue() && toCSSPrimitiveValue(start).isRect();
     bool endRect = end.isPrimitiveValue() && toCSSPrimitiveValue(end).isRect();