Updated SVGListPropertyHelper as per SVG2 Spec

Source/core/svg/SVGPathSegLinetoVerticalAbs.h

Index: Source/core/svg/SVGPathSegLinetoVerticalAbs.h
diff --git a/Source/core/svg/SVGPathSegLinetoVerticalAbs.h b/Source/core/svg/SVGPathSegLinetoVerticalAbs.h
index 5d4c353831715f215d702a3f97f37910dda9651d..4c081aa0ae22aabb957c69f4bace46be35b9b50a 100644
--- a/Source/core/svg/SVGPathSegLinetoVerticalAbs.h
+++ b/Source/core/svg/SVGPathSegLinetoVerticalAbs.h
@@ -34,6 +34,11 @@ public:
         return adoptRefWillBeNoop(new SVGPathSegLinetoVerticalAbs(element, y));
     }
 
+    PassRefPtrWillBeRawPtr<SVGPathSeg> clone() override
+    {
+        return adoptRefWillBeNoop(new SVGPathSegLinetoVerticalAbs(nullptr, y()));
+    }
+
 private:
     SVGPathSegLinetoVerticalAbs(SVGPathElement* element, float y)
         : SVGPathSegLinetoVertical(element, y) { }