CSSValue Immediates: Replace CSSPrimitiveValue usage with const references

Source/core/css/CSSProperty.h

Index: Source/core/css/CSSProperty.h
diff --git a/Source/core/css/CSSProperty.h b/Source/core/css/CSSProperty.h
index 2a2230055f81dacee3e0a6a7f747c3114efe399d..502f784f27fecdb60bdc70fa2cebf9b52d8d4801 100644
--- a/Source/core/css/CSSProperty.h
+++ b/Source/core/css/CSSProperty.h
@@ -56,14 +56,14 @@ struct StylePropertyMetadata {
 class CSSProperty {
     ALLOW_ONLY_INLINE_ALLOCATION();
 public:
-    CSSProperty(CSSPropertyID propertyID, CSSValue value, bool important = false, bool isSetFromShorthand = false, int indexInShorthandsVector = 0, bool implicit = false)
+    CSSProperty(CSSPropertyID propertyID, const CSSValue& value, bool important = false, bool isSetFromShorthand = false, int indexInShorthandsVector = 0, bool implicit = false)
         : m_metadata(propertyID, isSetFromShorthand, indexInShorthandsVector, important, implicit, CSSPropertyMetadata::isInheritedProperty(propertyID))
         , m_value(value)
     {
     }
 
     // FIXME: Remove this.
-    CSSProperty(StylePropertyMetadata metadata, CSSValue value)
+    CSSProperty(StylePropertyMetadata metadata, const CSSValue& value)
         : m_metadata(metadata)
         , m_value(value)
     {
@@ -74,7 +74,7 @@ public:
     CSSPropertyID shorthandID() const { return m_metadata.shorthandID(); }
     bool isImportant() const { return m_metadata.m_important; }
 
-    const CSSValue& value() const { return m_value; }
+    const CSSValue& value() const { return *m_value; }
 
     static CSSPropertyID resolveDirectionAwareProperty(CSSPropertyID, TextDirection, WritingMode);
     static bool isAffectedByAllProperty(CSSPropertyID);
@@ -87,7 +87,7 @@ public:
 
 private:
     StylePropertyMetadata m_metadata;
-    CSSValue m_value;
+    NullableCSSValue m_value;
 };
 
 } // namespace blink