Introduce CSS_VALUE_TYPE_CASTS macro to cast CSSValue

Source/core/css/CSSValue.h

Index: Source/core/css/CSSValue.h
diff --git a/Source/core/css/CSSValue.h b/Source/core/css/CSSValue.h
index a92bc86a5b532c845ed46447042e49ce06f66424..d62f81e2059fe60e408bad8b23d953423000d6a5 100644
--- a/Source/core/css/CSSValue.h
+++ b/Source/core/css/CSSValue.h
@@ -237,6 +237,20 @@ inline bool compareCSSValuePtr(const RefPtr<CSSValueType>& first, const RefPtr<C
     return first ? second && first->equals(*second) : !second;
 }
 
+#define DEFINE_CSS_VALUE_TYPE_CASTS(ValueTypeName) \
+inline const CSS##ValueTypeName* toCSS##ValueTypeName(const CSSValue* value) \
+{ \
+    ASSERT_WITH_SECURITY_IMPLICATION(!value || value->is##ValueTypeName()); \
+    return static_cast<const CSS##ValueTypeName*>(value); \
+} \
+inline CSS##ValueTypeName* toCSS##ValueTypeName(CSSValue* value) \
+{ \
+    ASSERT_WITH_SECURITY_IMPLICATION(!value || value->is##ValueTypeName()); \
+    return static_cast<CSS##ValueTypeName*>(value); \
+} \
+void toCSS##ValueTypeName(const CSS##ValueTypeName*); \
+void toCSS##ValueTypeName(const CSS##ValueTypeName&)
+
 } // namespace WebCore
 
 #endif // CSSValue_h