Updated SVGListPropertyHelper as per SVG2 Spec

Source/core/svg/properties/SVGListPropertyTearOffHelper.h

Index: Source/core/svg/properties/SVGListPropertyTearOffHelper.h
diff --git a/Source/core/svg/properties/SVGListPropertyTearOffHelper.h b/Source/core/svg/properties/SVGListPropertyTearOffHelper.h
index 08e46005a932fc9d9889d49543ebca9dc56f56df..d2cd09b2cc03e25085c529efe9084504038fb602 100644
--- a/Source/core/svg/properties/SVGListPropertyTearOffHelper.h
+++ b/Source/core/svg/properties/SVGListPropertyTearOffHelper.h
@@ -51,8 +51,9 @@ public:
         // |newItem| is immutable, OR
         // |newItem| belongs to a SVGElement, but it does not belong to an animated list
         // (for example: "textElement.x.baseVal.appendItem(rectElement.width.baseVal)")
-        if (newItem->isImmutable()
-            || (newItem->contextElement() && !newItem->target()->ownerList())) {
+        // Spec: If newItem is already in a list, then a new object is created with the same values as newItem and this item is inserted into the list.
+        // Otherwise, newItem itself is inserted into the list.
+        if (newItem->isImmutable() || newItem->target()->ownerList() || newItem->contextElement()) {
             // We have to copy the incoming |newItem|,
             // Otherwise we'll end up having two tearoffs that operate on the same SVGProperty. Consider the example below:
             // SVGRectElements SVGAnimatedLength 'width' property baseVal points to the same tear off object