CSSValue Immediates: Replace CSSPrimitiveValue usage with const references

Source/core/layout/svg/ReferenceFilterBuilder.cpp

Index: Source/core/layout/svg/ReferenceFilterBuilder.cpp
diff --git a/Source/core/layout/svg/ReferenceFilterBuilder.cpp b/Source/core/layout/svg/ReferenceFilterBuilder.cpp
index c426cc90db5239d3e391370745fa882f329c5aa8..9977c8771eb6f3b5cee3ccca17e700ea3d8ae91c 100644
--- a/Source/core/layout/svg/ReferenceFilterBuilder.cpp
+++ b/Source/core/layout/svg/ReferenceFilterBuilder.cpp
@@ -76,9 +76,9 @@ static EColorInterpolation colorInterpolationForElement(SVGElement& element, ECo
     // No layout has been performed, try to determine the property value
     // "manually" (used by external SVG files.)
     if (const StylePropertySet* propertySet = element.presentationAttributeStyle()) {
-        NullableCSSValue cssValue = propertySet->getPropertyCSSValue(CSSPropertyColorInterpolationFilters);
+        const NullableCSSValue& cssValue = propertySet->getPropertyCSSValue(CSSPropertyColorInterpolationFilters);
         if (cssValue && cssValue->isPrimitiveValue()) {
-            const CSSPrimitiveValue primitiveValue = toCSSPrimitiveValue(*cssValue);
+            const CSSPrimitiveValue& primitiveValue = toCSSPrimitiveValue(cssValue);
             return static_cast<EColorInterpolation>(primitiveValue);
         }
     }