Have page_with_touch_start_janking_main_thread.html work on desktop

page_with_touch_start_janking_main_thread.html currently does nothing on
desktop as the setting of ontouchstart seems to be ignored. I imagine this is due
to https://groups.google.com/a/chromium.org/d/msg/blink-dev/KV6kqDJpYiE/YFM28ZNBBAAJ

Bug: None
Change-Id: I7ec67e8f42445eec4583d1b6f5aae5e0ea2d7d9f
Reviewed-on: https://chromium-review.googlesource.com/c/1396326Reviewed-by: Ella Ge <eirage@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620028}

content/test/data/page_with_touch_start_janking_main_thread.html

@@ -10,10 +10,10 @@
 </body>
 <script>
 function setup() {
-  janktest.ontouchstart = function() {
+  document.getElementById('janktest').addEventListener('touchstart', (e) => {
     var end = performance.now() + 1200;
-    while (performance.now() < end) ;
-  };
+    while (performance.now() < end);
+  }, {passive: false});
 }
 </script>
 </html>