Bug 1685209 - Migrate helper_scroll_tables_perspective.html to async/await style. r=botond

Depends on D100897

Differential Revision: https://phabricator.services.mozilla.com/D100898

gfx/layers/apz/test/mochitest/helper_scroll_tables_perspective.html

@@ -4,18 +4,18 @@
   <script type="application/javascript" src="apz_test_utils.js"></script>
   <script src="/tests/SimpleTest/paint_listener.js"></script>
   <script type="application/javascript">
-function* test(testDriver) {
+async function test() {
   var subframe = document.getElementById("content-wrapper");
 
   // scroll over the middle of the subframe, to make sure it scrolls,
   // not the page
   var scrollPos = subframe.scrollTop;
-  yield moveMouseAndScrollWheelOver(subframe, 100, 100, testDriver);
+  await promiseMoveMouseAndScrollWheelOver(subframe, 100, 100);
   ok(subframe.scrollTop > scrollPos, "subframe scrolled after wheeling over it");
 }
 
 waitUntilApzStable()
-.then(runContinuation(test))
+.then(test)
 .then(subtestDone, subtestFailed);
 
   </script>