Improve cross-origin-subframe-for-scrolling layout test

third_party/WebKit/LayoutTests/http/tests/misc/resources/cross-origin-subframe-for-scrolling.html

Index: third_party/WebKit/LayoutTests/http/tests/misc/resources/cross-origin-subframe-for-scrolling.html
diff --git a/third_party/WebKit/LayoutTests/http/tests/misc/resources/cross-origin-subframe-for-scrolling.html b/third_party/WebKit/LayoutTests/http/tests/misc/resources/cross-origin-subframe-for-scrolling.html
index 75414848f7d7422ede192739fff1dab2f4cf88fa..605282697767432496dec1287e9caed205220905 100644
--- a/third_party/WebKit/LayoutTests/http/tests/misc/resources/cross-origin-subframe-for-scrolling.html
+++ b/third_party/WebKit/LayoutTests/http/tests/misc/resources/cross-origin-subframe-for-scrolling.html
@@ -3,8 +3,8 @@
 <div style="height: 300px"></div>
 
 <script>
-setPrintTestResultsLazily();
-self.jsTestIsAsync = true;
+var port;
+var frame_id;
 
 window.onload = (() => {
   if (!window.eventSender || !window.internals) {
@@ -16,13 +16,20 @@ window.onload = (() => {
 
 function handleMessage(event) {
   if (event.data.hasOwnProperty('scrollBy')) {
+    port = event.source;
+    frame_id = event.data.frame_id;
     eventSender.mouseMoveTo(event.data.left + 5, event.data.top + 5);
     eventSender.mouseScrollBy(0, event.data.scrollBy);
-    requestAnimationFrame(() => {setTimeout(() => {event.source.postMessage("", "*")}, 500)});
   } else {
     event.source.postMessage({scrollTop: document.documentElement.scrollTop}, "*");
   }
 }
 
+window.onscroll = (() => {
+  if (port) {
+    port.postMessage({scrolled: frame_id}, "*");

[bokan, 2017/01/20 18:13:26]

Can't we simplify this and just post the scrollTop in here?

+  }
+});
+
 window.addEventListener("message", handleMessage);
 </script>