Updated SVGListPropertyHelper as per SVG2 Spec

LayoutTests/svg/dom/SVGLengthList-insertItemBefore.xhtml

Index: LayoutTests/svg/dom/SVGLengthList-insertItemBefore.xhtml
diff --git a/LayoutTests/svg/dom/SVGLengthList-insertItemBefore.xhtml b/LayoutTests/svg/dom/SVGLengthList-insertItemBefore.xhtml
index 8546ce4e1c6056fc8844f689448270663fae0e89..c341555a3c4f93e4be030c5d346c6d3ba219eded 100644
--- a/LayoutTests/svg/dom/SVGLengthList-insertItemBefore.xhtml
+++ b/LayoutTests/svg/dom/SVGLengthList-insertItemBefore.xhtml
@@ -96,31 +96,34 @@
     shouldBe("text1.x.baseVal.getItem(5).value", "50");
     shouldThrow("text1.x.baseVal.getItem(6)");
 
-    // Spec: If newItem is already in a list, it is removed from its previous list before it is inserted into this list.
-    // Spec: If the item is already in this list, note that the index of the item to insert before is before the removal of the item. 
+    // 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.. 
     debug("");
-    debug("Insert item 'newLength3' at position=1, between '100' and '500', remove it from the old position=2 afterwards.");
+    debug("Insert item 'newLength3' at position=1, between '100' and '500', should not remove it from the old position=2 afterwards.");
     shouldBe("text1.x.baseVal.insertItemBefore(newLength3, 1)", "newLength3");
-    shouldBe("text1.x.baseVal.numberOfItems", "6");
+    shouldBe("text1.x.baseVal.numberOfItems", "7");
     shouldBe("text1.x.baseVal.getItem(0).value", "100");
     shouldBe("text1.x.baseVal.getItem(1).value", "150");
     shouldBe("text1.x.baseVal.getItem(2).value", "500");
-    shouldBe("text1.x.baseVal.getItem(3).value", "1000");
-    shouldBe("text1.x.baseVal.getItem(4).value", "1500");
-    shouldBe("text1.x.baseVal.getItem(5).value", "50");
-    shouldThrow("text1.x.baseVal.getItem(6)");
+    shouldBe("text1.x.baseVal.getItem(3).value", "150");
+    shouldBe("text1.x.baseVal.getItem(4).value", "1000");
+    shouldBe("text1.x.baseVal.getItem(5).value", "1500");
+    shouldBe("text1.x.baseVal.getItem(6).value", "50");
+    shouldThrow("text1.x.baseVal.getItem(7)");
 
     debug("");
-    debug("Insert item 'newLength3' at position=0, before '100', remove it from the old position=5 afterwards.");
+    debug("Insert item 'newLength1' at position=0, before '100', should not remove it from the old position=6 afterwards.");
     shouldBe("text1.x.baseVal.insertItemBefore(newLength1, 0)", "newLength1");
-    shouldBe("text1.x.baseVal.numberOfItems", "6");
+    shouldBe("text1.x.baseVal.numberOfItems", "8");
     shouldBe("text1.x.baseVal.getItem(0).value", "50");
     shouldBe("text1.x.baseVal.getItem(1).value", "100");
     shouldBe("text1.x.baseVal.getItem(2).value", "150");
     shouldBe("text1.x.baseVal.getItem(3).value", "500");
-    shouldBe("text1.x.baseVal.getItem(4).value", "1000");
-    shouldBe("text1.x.baseVal.getItem(5).value", "1500");
-    shouldThrow("text1.x.baseVal.getItem(6)");
+    shouldBe("text1.x.baseVal.getItem(4).value", "150");
+    shouldBe("text1.x.baseVal.getItem(5).value", "1000");
+    shouldBe("text1.x.baseVal.getItem(6).value", "1500");
+    shouldBe("text1.x.baseVal.getItem(7).value", "50");
+    shouldThrow("text1.x.baseVal.getItem(8)");
 
     debug("");
     debug("The test passes if you only see 'PASS' messages, and both text elements on top look the same");