Bug 1647474 - Wait for frame callbacks on the right window. r=kats

Quite obvious in hindsight :(

Differential Revision: https://phabricator.services.mozilla.com/D81128

layout/forms/test/test_bug564115.html

@@ -25,8 +25,8 @@ addLoadEvent(function() {
 
     // Focus the input box, and wait for the focus to actually happen
     input.focus();
-    requestAnimationFrame(function() {
-      requestAnimationFrame(function() {
+    win.requestAnimationFrame(function() {
+      win.requestAnimationFrame(function() {
         // Scroll down a bit
         win.scrollTo(0, 5000);