The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d2d014a7e9148b0c455736957f1714932f5778b9

commit d2d014a7e9148b0c455736957f1714932f5778b9
Author: Jordy Greenblatt <jordynass@chromium.org>
Date: Thu Sep 20 19:42:10 2018

[CrOS MultiDevice] Block false Settings error from ambiguous listener.

The settings-multidevice-setup-page listens for the event 'close'
as a proxy for the password prompt being confirmed. However, the
event type 'close' is ubiquitous to cr-dialog so it also fires when
the forget device dialog is closed on the subpage, which causes the
assertion "assert(this.featureToBeEnabledOnceAuthenticated_ !== null)"
in SettingsMultidevicePageElement.onPasswordPromptDialogClose() to
fail.

This CL only calls onPasswordPromptDialogClose_ if the close event came
from the MultiDevice page's password prompt and stops the event's
propagation.

Bug:  887160 
Change-Id: I5740061c8f9e08ee5ba9e8d99862bcec6b0a6677
Reviewed-on: https://chromium-review.googlesource.com/1235321
Commit-Queue: Jordy Greenblatt <jordynass@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592908}
[modify] https://crrev.com/d2d014a7e9148b0c455736957f1714932f5778b9/chrome/browser/resources/settings/multidevice_page/multidevice_page.html
[modify] https://crrev.com/d2d014a7e9148b0c455736957f1714932f5778b9/chrome/browser/resources/settings/multidevice_page/multidevice_page.js
[modify] https://crrev.com/d2d014a7e9148b0c455736957f1714932f5778b9/chrome/test/data/webui/settings/multidevice_page_tests.js