CSSValue Immediates: Replace CSSPrimitiveValue usage with const references

Source/core/css/CSSValueList.h

Index: Source/core/css/CSSValueList.h
diff --git a/Source/core/css/CSSValueList.h b/Source/core/css/CSSValueList.h
index 12d0e62c2d1e7d4c0006241f74645fc9f8422b33..66655029f4a00a61d044ba56adee4b5930a0e94a 100644
--- a/Source/core/css/CSSValueList.h
+++ b/Source/core/css/CSSValueList.h
@@ -52,15 +52,13 @@ public:
     const_iterator end() const { return m_values.end(); }
 
     size_t length() const { return m_values.size(); }
-    CSSValue item(size_t index) { return m_values[index]; }
-    const CSSValue item(size_t index) const { return m_values[index]; }
-    NullableCSSValue itemWithBoundsCheck(size_t index) { return index < m_values.size() ? NullableCSSValue(m_values[index]) : nullptr; }
+    const CSSValue& item(size_t index) const { return m_values[index]; }
     const NullableCSSValue itemWithBoundsCheck(size_t index) const { return index < m_values.size() ? NullableCSSValue(m_values[index]) : nullptr; }
 
-    void append(CSSValue value) { m_values.append(value); }
-    void prepend(CSSValue value) { m_values.prepend(value); }
-    bool removeAll(CSSValue);
-    bool hasValue(CSSValue) const;
+    void append(const CSSValue& value) { m_values.append(value); }
+    void prepend(const CSSValue& value) { m_values.prepend(value); }
+    bool removeAll(const CSSValue&);
+    bool hasValue(const CSSValue&) const;
     PassRefPtrWillBeRawPtr<CSSValueList> copy();
 
     String customCSSText() const;