Refactor of various layout tests to use RAF

LayoutTests/svg/animations/smil-leak-element-instances-noBaseValRef.svg

 <svg id="svg" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" onload="load()">
 <defs>
     <rect id="rect" width="100" height="100" />
 </defs>
 <g id="g"/>
 <text x="50" y="50" id="log"/>
 <script xlink:href="../../resources/js-test.js"></script>
 <script id="script">
 <![CDATA[
 
@@ skipping 41 matching lines @@
 
             testRunner.notifyDone();
         });
     });
 }
 
 function startTest() {
     for (var i = 0; i < 100; i++)
         g.appendChild(createAnimatedRectInstance());
 
-    setTimeout(cleanup, 0);
+    requestAnimationFrame(cleanup);
 }
 
 function load() {
     if (window.testRunner && window.GCController && window.internals) {
         testRunner.dumpAsText();
         testRunner.waitUntilDone();
     } else {
         log("This test only works when run with the testRunner, GCController, and internals available.");
         return;
     }
 
-    setTimeout(startTest, 0);
+    requestAnimationFrame(startTest);
 }
 ]]>
 </script>
 </svg>