Reverting https://chromium-review.googlesource.com/c/chromium/src/+/691794, which looks like the culprit.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6ad728b1ecd61106e9543493f4a9967b3bc0c21f

commit 6ad728b1ecd61106e9543493f4a9967b3bc0c21f
Author: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Date: Fri Sep 29 08:13:37 2017

sheriff: Disable PasswordsAndFormsBrowserTest.uiTests

TBR=dpapad@chromium.org

Bug:  770047 
Change-Id: Iced8b09b937f2a6b202bea47b99dcf6fbe137749
Reviewed-on: https://chromium-review.googlesource.com/691694
Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505329}
[modify] https://crrev.com/6ad728b1ecd61106e9543493f4a9967b3bc0c21f/chrome/test/data/webui/settings/passwords_and_forms_browsertest.js

I'm pretty sure my revert was enough; so I'm reverting the disabling. :)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d0e58aafd37f0fa510ebcff97494cb624bbb37b9

commit d0e58aafd37f0fa510ebcff97494cb624bbb37b9
Author: Mike West <mkwst@chromium.org>
Date: Fri Sep 29 11:41:27 2017

Revert "sheriff: Disable PasswordsAndFormsBrowserTest.uiTests"

This reverts commit 6ad728b1ecd61106e9543493f4a9967b3bc0c21f.

Reason for revert:
The revert in https://chromium-review.googlesource.com/c/chromium/src/+/691794 should have fixed
the underlying problem. So we don't need to disable the test. :)

Original change's description:
> sheriff: Disable PasswordsAndFormsBrowserTest.uiTests
> 
> TBR=dpapad@chromium.org
> 
> Bug:  770047 
> Change-Id: Iced8b09b937f2a6b202bea47b99dcf6fbe137749
> Reviewed-on: https://chromium-review.googlesource.com/691694
> Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
> Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#505329}

TBR=dpapad@chromium.org,ortuno@chromium.org

Change-Id: I60d94fdf0cf77ed04d0b02f4193b54be66e270bd
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug:  770047 
Reviewed-on: https://chromium-review.googlesource.com/691994
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Mike West <mkwst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505347}
[modify] https://crrev.com/d0e58aafd37f0fa510ebcff97494cb624bbb37b9/chrome/test/data/webui/settings/passwords_and_forms_browsertest.js

Removing sheriff label.

There is nothing to do here. See explanation of why it broke and how the revert fixed it at https://chromium-review.googlesource.com/c/chromium/src/+/691794#message-9fef1c717cdb1180530094bcb07264216bda5b58.

https://chromium-review.googlesource.com/c/chromium/src/+/693040 is adding the missing dependency which should enable relanding the original CL.