Remove display() from more layout tests

LayoutTests/fast/layers/add-layer-with-nested-stacking.html

 <style>
 #test {
     overflow: hidden; /* Required to reproduce. */
 }
 
 #test::before {
     content: "";  /* Some content required to reproduce. */
     opacity: 0.999; /* Required to reproduce. */
     display: block;
     width: 100px;
     height: 100px;
     background-color: green;
 }
 </style>
 <div id="test" style="display: none"></div>
+<script src="../../resources/run-after-display.js"></script>
 <script type="text/javascript">
-    function test()
-    {
+    if (window.testRunner)
+        testRunner.waitUntilDone();
+    runAfterDisplay(function() {
         document.getElementById("test").style.display = "block";
-    }
-
-    if (!window.testRunner)
-        setTimeout(test, 0);
-    else {
-        document.body.offsetTop;
-        testRunner.display();
-        test();
-    }
+        if (window.testRunner)
+            testRunner.notifyDone();
+    });
 </script>