CSSValue Immediates: Replace CSSValue usage with const references

Source/core/css/StylePropertySerializer.h

Index: Source/core/css/StylePropertySerializer.h
diff --git a/Source/core/css/StylePropertySerializer.h b/Source/core/css/StylePropertySerializer.h
index 310e1b4aec0ac6e0e1f9c457f65732f122ae00ff..e1e4f9e20807fd38c84f452d0e2de1e31b4d7bf1 100644
--- a/Source/core/css/StylePropertySerializer.h
+++ b/Source/core/css/StylePropertySerializer.h
@@ -65,7 +65,7 @@ private:
             , m_isImplicit(property.isImplicit())
             , m_isInherited(property.isInherited()) { }
 
-        PropertyValueForSerializer(CSSPropertyID id, const CSSValue value, bool isImportant)
+        PropertyValueForSerializer(CSSPropertyID id, const CSSValue& value, bool isImportant)
             : m_value(value)
             , m_id(id)
             , m_isImportant(isImportant)
@@ -73,7 +73,7 @@ private:
             , m_isInherited(value.isInheritedValue()) { }
 
         CSSPropertyID id() const { return m_id; }
-        const CSSValue value() const { return m_value; }
+        const CSSValue& value() const { return m_value; }
         bool isImportant() const { return m_isImportant; }
         bool isImplicit() const { return m_isImplicit; }
         bool isInherited() const { return m_isInherited; }