Avoid using instanceRoot in layout tests

LayoutTests/svg/custom/use-on-use-with-child.svg

 <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg11.dtd"> 
 <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"> 
     <title id="viewer_title">Mouse Over the Red Dot And Wait For the Crash</title> 
     <defs> 
         <circle id="rim" cx="0" cy="0" r="70"/> 
         <g id="loupePlus"> 
             <use id="useRim" xlink:href="#rim" fill="#e33c31"> 
                 <set />
             </use> 
         </g> 
     </defs> 
 
     <use id="zoomplus" xlink:href="#loupePlus" x="300" y="300" >
     </use> 
     <foreignObject><pre id="console" xmlns="http://www.w3.org/1999/xhtml"/></foreignObject>
     <script>
         function makeCrash(){
             if (window.eventSender) {
                 eventSender.dragMode = false;
                 eventSender.mouseMoveTo(300, 300);
                 eventSender.mouseDown();
                 eventSender.mouseUp();
             }
         }
         // If you like, you can make a crash.
         // makeCrash();
 
         var console = document.getElementById("console");
-        function println(string)
+        function print(string)
         {
-            console.textContent += string + '\n';
+            console.textContent += string;
         }
 
         function printInstanceTree( obj, indent )
         {
             indent += "     ";
-            println(indent + "id = " + obj.correspondingElement.id + "  this = " + obj + "  correspondingElement = " + obj.correspondingElement);
+            print(indent);
+            if (obj.id) { 
+                print(" id = " + obj.id);
+            }
+            print(" this = " + obj + "\n");
             for (var m = obj.firstChild; m != null; m = m.nextSibling ) {
                 printInstanceTree(m, indent);
             }
         }
-        var useobj = document.getElementById("zoomplus").instanceRoot;
-        println("The instance tree of use element zoomplus:\n");
+        var useobj = internals.shadowRoot(document.getElementById("zoomplus"));
+        print("The instance tree of use element zoomplus:\n");
         printInstanceTree(useobj,"");
 
         if (window.testRunner){
             testRunner.dumpAsText();
         }
 
   </script>
 </svg>