Findit identified the culprit r575469 with confidence 70.0% in the config "tryserver.chromium.chromiumos / linux-chromeos-rel"
based on the flakiness trend:

https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVy1QELEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCKeAWNocm9taXVtLmNocm9taXVtb3MvbGludXgtY2hyb21lb3MtcmVsLzEwNzgwL2ludGVyYWN0aXZlX3VpX3Rlc3RzL1FXeHNMMEYxZEc5bWFXeHNTVzUwWlhKaFkzUnBkbVZKYzI5c1lYUnBiMjVVWlhOMExrUmxiR1YwYVc1blJuSmhiV1ZWYm1SbGNsTjFaMmRsYzNScGIyNHZNUT09DAsSE01hc3RlckZsYWtlQW5hbHlzaXMYAQw

If the culprit above is wrong, please file a bug using this link and hit submit:
https://bugs.chromium.org/p/chromium/issues/entry?status=Unconfirmed&labels=Pri-1,Test-Findit-Wrong&components=Tools%3ETest%3EFindit%3EFlakiness&summary=%5BFindit%5D%20Flake%20Analyzer%20-%20Wrong%20result%20for%20All/AutofillInteractiveIsolationTest.DeletingFrameUnderSuggestion/1&comment=Link%20to%20Analysis%3A%20https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVy1QELEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCKeAWNocm9taXVtLmNocm9taXVtb3MvbGludXgtY2hyb21lb3MtcmVsLzEwNzgwL2ludGVyYWN0aXZlX3VpX3Rlc3RzL1FXeHNMMEYxZEc5bWFXeHNTVzUwWlhKaFkzUnBkbVZKYzI5c1lYUnBiMjVVWlhOMExrUmxiR1YwYVc1blJuSmhiV1ZWYm1SbGNsTjFaMmRsYzNScGIyNHZNUT09DAsSE01hc3RlckZsYWtlQW5hbHlzaXMYAQw

Automatically posted by the findit-for-me app (https://goo.gl/Ot9f7N).

On it. Will revert the cl if I can't find a quick fix in a reasonable time.

I fix is under review: https://chromium-review.googlesource.com/c/chromium/src/+/1140284

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c2869e1e867c8adf275fd925a6d40cac049e8134

commit c2869e1e867c8adf275fd925a6d40cac049e8134
Author: Fabio Tirelo <ftirelo@chromium.org>
Date: Tue Jul 17 18:58:47 2018

[AF] Cleanup rows when the popup is hidden

This fixes a flaky test on ChromeOS, in which a mouse exit event can be
received by a row after the popup is hidden (in the test in case, this
happened when the frame that contained the dropdown was deleted).

The solution here consists of not giving rows direct access to the
controller; now they need to use an accessor method in the native view,
which will return nullptr after the popup is hidden.

As a safety measure, also protected other accesses to the controller,
except on CreateContent(), which is called when a row is being created,
and the controller's existence is guaranteed.

Bug:  864477 
Change-Id: I8be9be974065543ca9da6ea165365ed7777e70b7
Reviewed-on: https://chromium-review.googlesource.com/1140284
Commit-Queue: Fabio Tirelo <ftirelo@chromium.org>
Reviewed-by: Tommy Martino <tmartino@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575739}
[modify] https://crrev.com/c2869e1e867c8adf275fd925a6d40cac049e8134/chrome/browser/ui/views/autofill/autofill_popup_view_native_views.cc
[modify] https://crrev.com/c2869e1e867c8adf275fd925a6d40cac049e8134/chrome/browser/ui/views/autofill/autofill_popup_view_native_views.h