Updated SVGListPropertyHelper as per SVG2 Spec

Source/core/svg/SVGPathSegArcRel.h

Index: Source/core/svg/SVGPathSegArcRel.h
diff --git a/Source/core/svg/SVGPathSegArcRel.h b/Source/core/svg/SVGPathSegArcRel.h
index f1c6ad24fe2e2a19646402b46eb1db12e253e1a5..b4b426b7162cfc43ee1d4a7ee7e3ef202d6f4cc5 100644
--- a/Source/core/svg/SVGPathSegArcRel.h
+++ b/Source/core/svg/SVGPathSegArcRel.h
@@ -34,6 +34,11 @@ public:
         return adoptRefWillBeNoop(new SVGPathSegArcRel(element, x, y, r1, r2, angle, largeArcFlag, sweepFlag));
     }
 
+    PassRefPtrWillBeRawPtr<SVGPathSeg> clone() override
+    {
+        return adoptRefWillBeNoop(new SVGPathSegArcRel(nullptr, x(), y(), r1(), r2(), angle(), largeArcFlag(), sweepFlag()));
+    }
+
 private:
     SVGPathSegArcRel(SVGPathElement* element, float x, float y, float r1, float r2, float angle, bool largeArcFlag, bool sweepFlag)
         : SVGPathSegArc(element, x, y, r1, r2, angle, largeArcFlag, sweepFlag) { }