CSSValue Immediates: Replace CSSPrimitiveValue usage with const references

Source/core/css/Pair.h

Index: Source/core/css/Pair.h
diff --git a/Source/core/css/Pair.h b/Source/core/css/Pair.h
index f9f20c2d757418469c2fa8fd117b6ca9ba7b0f09..f552cde11b89644aa0c971bc7ca376db19acffe8 100644
--- a/Source/core/css/Pair.h
+++ b/Source/core/css/Pair.h
@@ -37,18 +37,18 @@ class CORE_EXPORT Pair final : public RefCountedWillBeGarbageCollectedFinalized<
 public:
     enum IdenticalValuesPolicy { DropIdenticalValues, KeepIdenticalValues };
 
-    static PassRefPtrWillBeRawPtr<Pair> create(CSSPrimitiveValue first, CSSPrimitiveValue second,
+    static PassRefPtrWillBeRawPtr<Pair> create(const CSSPrimitiveValue& first, const CSSPrimitiveValue& second,
         IdenticalValuesPolicy identicalValuesPolicy)
     {
         return adoptRefWillBeNoop(new Pair(first, second, identicalValuesPolicy));
     }
 
-    NullableCSSValue first() const { return m_first; }
-    NullableCSSValue second() const { return m_second; }
+    const CSSPrimitiveValue& first() const { return toCSSPrimitiveValue(m_first); }
+    const CSSPrimitiveValue& second() const { return toCSSPrimitiveValue(m_second); }
 
     String cssText() const
     {
-        return generateCSSString(first()->cssText(), second()->cssText(), m_identicalValuesPolicy);
+        return generateCSSString(first().cssText(), second().cssText(), m_identicalValuesPolicy);
     }
 
     bool equals(const Pair& other) const
@@ -61,7 +61,7 @@ public:
     DECLARE_TRACE();
 
 private:
-    Pair(CSSPrimitiveValue first, CSSPrimitiveValue second, IdenticalValuesPolicy identicalValuesPolicy)
+    Pair(const CSSPrimitiveValue& first, const CSSPrimitiveValue& second, IdenticalValuesPolicy identicalValuesPolicy)
         : m_first(first)
         , m_second(second)
         , m_identicalValuesPolicy(identicalValuesPolicy) { }
@@ -73,8 +73,8 @@ private:
         return first + ' ' + second;
     }
 
-    NullableCSSValue m_first;
-    NullableCSSValue m_second;
+    CSSValue m_first;
+    CSSValue m_second;
     IdenticalValuesPolicy m_identicalValuesPolicy;
 };