CSSValue Immediates: Replace CSSPrimitiveValue usage with const references

Source/core/css/CSSValue.h

Index: Source/core/css/CSSValue.h
diff --git a/Source/core/css/CSSValue.h b/Source/core/css/CSSValue.h
index b9d3b052e55182e2427b6a6f048856802d2d3724..8e8ec00fd043e8a2beaafbaab338c7392da5f8ae 100644
--- a/Source/core/css/CSSValue.h
+++ b/Source/core/css/CSSValue.h
@@ -397,12 +397,16 @@ inline bool compareCSSValueVector(const WillBeHeapVector<CSSValue, inlineCapacit
         return static_cast<thisType*>(value.get()); \
     }
 
-// Returns by value on purpose.
 inline const CSSPrimitiveValue& toCSSPrimitiveValue(const CSSValue& value)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(value.isPrimitiveValue());
     return *reinterpret_cast<const CSSPrimitiveValue*>(&value);
 }
+inline const CSSPrimitiveValue& toCSSPrimitiveValue(const NullableCSSValue& value)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(value && value->isPrimitiveValue());
+    return *reinterpret_cast<const CSSPrimitiveValue*>(&value);
+}
 /*
 inline CSSPrimitiveValue& toCSSPrimitiveValue(const CSSValue& value)
 {