Make errors appear in the right place

Author: TimothyGu

html/webappapis/dynamic-markup-insertion/opening-the-input-stream/event-listeners.window.js

@@ -59,15 +59,18 @@ test(t => {
   frame.contentDocument.close();
 }, "IDL attribute event handlers are to be deactivated");
 
+var thrower;
+
 test(t => {
   const frame = document.body.appendChild(document.createElement("iframe")),
         body = frame.contentDocument.body;
   t.add_cleanup(() => frame.remove());
   const div = body.appendChild(frame.contentDocument.createElement("div"));
-  div.setAttribute("onclick", "throw new Error('element event listener not removed')");
+  thrower = t.step_func(() => { throw new Error('element event listener not removed'); });
+  div.setAttribute("onclick", "parent.thrower()");
   assert_not_equals(div.onclick, null);
   frame.contentDocument.open();
-  assert_equals(div.getAttribute("onclick"), "throw new Error('element event listener not removed')");
+  assert_equals(div.getAttribute("onclick"), "parent.thrower()");
   assert_equals(div.onclick, null);
   const e = frame.contentDocument.createEvent("mouseevents")
   e.initEvent("click", false, false);