Actually, looks like send/unsend checkbox doesn't work either.

I suspect this is my fault. ;) If you don't have time to fix it reassign to me.

I'm looking at it and also  bug 643366  (they are connected, in a way)

Adding Privacy label. The checkbox doesn't work on a captive portal interstitial, meaning users who already opted in can't opt out of reporting while on this interstitial. 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ee53d14732a274057e9ce51c1d07d87fc7ffc90e

commit ee53d14732a274057e9ce51c1d07d87fc7ffc90e
Author: meacer <meacer@chromium.org>
Date: Tue Oct 04 00:38:09 2016

Fix privacy policy link in captive portal interstitials.

BUG= 642911 

Review-Url: https://codereview.chromium.org/2302623002
Cr-Commit-Position: refs/heads/master@{#422634}

[modify] https://crrev.com/ee53d14732a274057e9ce51c1d07d87fc7ffc90e/chrome/browser/ssl/captive_portal_blocking_page.cc

This was a relatively large change that required two other CLs, so I'm not going to request a merge.