Fix some async repaint tests

LayoutTests/svg/custom/resource-client-removal.svg

 <svg width="100%" height="100%" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" onload="runRepaintAndPixelTest()">
 <script xlink:href="../../fast/repaint/resources/text-based-repaint.js"/>
 <script>
 <![CDATA[
+window.testIsAsync = true;
 function repaintTest() {
     container = document.getElementById("inneruse");
     stop = document.getElementById("offset");
-    if (window.testRunner)
-        testRunner.waitUntilDone();
     setTimeout(offset, 0);
 }
 var turns = 5;
 function offset(){
     container.setAttribute ("transform", "");
     stop.setAttribute ("offset", "1.0");
     turns--;
     if (turns > 0)
         window.setTimeout("offset()", 0)
-    else if (window.testRunner)
-        testRunner.notifyDone();
+    else
+        finishRepaintTest();
 }
 ]]>
 </script>
 <defs>
 <linearGradient id="grad">
   <stop offset="0" style="stop-color: green"/>
   <stop id="offset" offset="1" style="stop-color: green"/>
 </linearGradient> 
 <path id="hp" d="M 0 0 L 100 0 L 100 100 L 0 100" />
 </defs>
 <g id="inneruse">
 <use xlink:href="#hp" style="fill:url(#grad)"/>
 </g>
 <use xlink:href="#inneruse" style="fill:url(#grad)"/> 
 </svg>