Instead, I get this error in the console:

POST https://codereview.chromium.org/2865233003/edit_flags 500 ()
(anonymous) @ cr-app.vulcanized.html?v=cc6ac46:1517
sendInternal @ cr-app.vulcanized.html?v=cc6ac46:1504
(anonymous) @ cr-app.vulcanized.html?v=cc6ac46:1530
Promise resolved (async)
xhr.onload @ cr-app.vulcanized.html?v=cc6ac46:1464
XMLHttpRequest.send (async)
(anonymous) @ cr-app.vulcanized.html?v=cc6ac46:1462
loadResource @ cr-app.vulcanized.html?v=cc6ac46:1458
loadJSON @ cr-app.vulcanized.html?v=cc6ac46:1490
User.loadCurrentUser @ cr-app.vulcanized.html?v=cc6ac46:2960
sendFormData @ cr-app.vulcanized.html?v=cc6ac46:1528
Issue.setFlags @ cr-app.vulcanized.html?v=cc6ac46:1880
(anonymous) @ cr-app.vulcanized.html?v=cc6ac46:12730
Promise resolved (async)
xhr.onload @ cr-app.vulcanized.html?v=cc6ac46:1464
XMLHttpRequest.send (async)
(anonymous) @ cr-app.vulcanized.html?v=cc6ac46:1462
loadResource @ cr-app.vulcanized.html?v=cc6ac46:1458
loadJSON @ cr-app.vulcanized.html?v=cc6ac46:1490
TryServers.loadDetails @ cr-app.vulcanized.html?v=cc6ac46:2865
retryFailedTryJobs @ cr-app.vulcanized.html?v=cc6ac46:12729
dispatchMethod @ cr-app.vulcanized.html?v=cc6ac46:496
(anonymous) @ cr-app.vulcanized.html?v=cc6ac46:497
fire @ cr-app.vulcanized.html?v=cc6ac46:496
handleRetryFailedTryJobs @ cr-app.vulcanized.html?v=cc6ac46:10164
dispatchMethod @ cr-app.vulcanized.html?v=cc6ac46:496
(anonymous) @ cr-app.vulcanized.html?v=cc6ac46:497
up @ cr-app.vulcanized.html?v=cc6ac46:494
gestureTrigger @ cr-app.vulcanized.html?v=cc6ac46:494
requestAnimationFrame (async)
fillGestureQueue @ cr-app.vulcanized.html?v=cc6ac46:494
dispatchEvent @ cr-app.vulcanized.html?v=cc6ac46:494
fireEvent @ cr-app.vulcanized.html?v=cc6ac46:494
up @ cr-app.vulcanized.html?v=cc6ac46:494
pointerup @ cr-app.vulcanized.html?v=cc6ac46:494
eventHandler @ cr-app.vulcanized.html?v=cc6ac46:494