CSSValue Immediates: Replace CSSValue usage with const references

Source/core/css/CSSCrossfadeValue.h

Index: Source/core/css/CSSCrossfadeValue.h
diff --git a/Source/core/css/CSSCrossfadeValue.h b/Source/core/css/CSSCrossfadeValue.h
index 7d581ea976af58a089587b6bd926bda746502497..8a7911b746ff97e4a2245d85616faa9a30851e6e 100644
--- a/Source/core/css/CSSCrossfadeValue.h
+++ b/Source/core/css/CSSCrossfadeValue.h
@@ -42,7 +42,7 @@ class LayoutObject;
 class CSSCrossfadeValue final : public CSSImageGeneratorValue {
     friend class CrossfadeSubimageObserverProxy;
 public:
-    static PassRefPtrWillBeRawPtr<CSSCrossfadeValue> create(CSSValue fromValue, CSSValue toValue)
+    static PassRefPtrWillBeRawPtr<CSSCrossfadeValue> create(const CSSValue& fromValue, const CSSValue& toValue)
     {
         return adoptRefWillBeNoop(new CSSCrossfadeValue(fromValue, toValue));
     }
@@ -74,7 +74,7 @@ public:
     DECLARE_TRACE_AFTER_DISPATCH();
 
 private:
-    CSSCrossfadeValue(CSSValue fromValue, CSSValue toValue)
+    CSSCrossfadeValue(const CSSValue& fromValue, const CSSValue& toValue)
         : CSSImageGeneratorValue(CrossfadeClass)
         , m_fromValue(fromValue)
         , m_toValue(toValue)