The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3436e1746ad149b739a244401d24a10964c2b560

commit 3436e1746ad149b739a244401d24a10964c2b560
Author: Devlin Cronin <rdevlin.cronin@chromium.org>
Date: Tue Aug 29 14:24:46 2017

[Extensions] De-flake ChromeUpdatesEventsApiTest.ChromeUpdates

ChromeUpdatesEventsApiTest.ChromeUpdates waits for a message to be
sent from an extension background page when it's woken up for a
chrome_updated event. However, there's a chance that the extension
could already have woken up and received the event before we can
register an extension listener.

Remove the message listening aspect, since there's not a good way of
ensuring determinism while testing it, and instead rely on the views
created for the given extensions (which should be sufficient).

Bug:  759546 
Change-Id: I4d0afa89139b905710cba434758b8f8121fcb154
Reviewed-on: https://chromium-review.googlesource.com/639355
Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#498104}
[modify] https://crrev.com/3436e1746ad149b739a244401d24a10964c2b560/chrome/browser/extensions/events_apitest.cc
[modify] https://crrev.com/3436e1746ad149b739a244401d24a10964c2b560/chrome/test/data/extensions/api_test/lazy_events/chrome_updates/listener/background.js
[modify] https://crrev.com/3436e1746ad149b739a244401d24a10964c2b560/chrome/test/data/extensions/api_test/lazy_events/chrome_updates/non_listener/background.js

Looks like this is fixed now, I don't see the same error on the bot anymore?
I'll leave it up to you, removing sheriff label.