CSSValue Immediates: Replace CSSPrimitiveValue usage with const references

Source/core/css/CSSValueList.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
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     {
         return adoptRefWillBeNoop(new CSSValueList(SlashSeparator));
     }
 
     iterator begin() { return m_values.begin(); }
     iterator end() { return m_values.end(); }
     const_iterator begin() const { return m_values.begin(); }
     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;
     bool equals(const CSSValueList&) const;
 
     bool hasFailedOrCanceledSubresources() const;
 
     DECLARE_TRACE_AFTER_DISPATCH();
 
 protected:
     CSSValueList(ClassType, ValueListSeparator);
 
 private:
     explicit CSSValueList(ValueListSeparator);
 
     WillBeHeapVector<CSSValue, 4> m_values;
 };
 
 DEFINE_CSS_VALUE_TYPE_CASTS(CSSValueList, isValueList());
 
 } // namespace blink
 
 #endif // CSSValueList_h