The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/83eea24bb70cd3acb379a92e45003e5aa03075a7

commit 83eea24bb70cd3acb379a92e45003e5aa03075a7
Author: Tatsuhisa Yamaguchi <yamaguchi@google.com>
Date: Tue May 08 11:59:09 2018

Prevent runtime errors on suspend events.

unpacker.app.onSuspend was removed at f878141 and no longer exists.
https://chromium-review.googlesource.com/940742

Bug:  839158 , 789073 , 803752 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I973b7728095cddcceab2e58c06ca07986a6bd9e6
Reviewed-on: https://chromium-review.googlesource.com/1049417
Commit-Queue: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
Reviewed-by: Yuki Awano <yawano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556763}
[modify] https://crrev.com/83eea24bb70cd3acb379a92e45003e5aa03075a7/chrome/browser/resources/chromeos/zip_archiver/js/background.js

I think this has been resolved by the revision.
Which was the test case in browser_tests that had the error message?

Any fo the ones that use NaCl. "/FileManagerBrowserTest*"

I went and read went LOGs for ~10min to see if I could find one and failed.

Since you have removed the offending code, we can just close here since there is truck load of other LOG error messages we should go fix.

Found one: VideoPlayerBrowserTest.OpenSingleVideoOnDownloads (CRASHED) ASAN
  http://build.chromium.org/p/chromium.memory/builders/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20(1)/builds/27201

Build log:

[28281:28281:0426/011811.065102:INFO:CONSOLE(0)] "Error in event handler for runtime.onSuspend: TypeError: The first argument is the receiver and must be an object", source: chrome-extension://dmboannefpncccogfdikhmhpmdnddgoe/_generated_background_page.html (0)
[28281:28281:0426/011811.583009:INFO:CONSOLE(0)] "[SUCCESS] [openSingleVideoOnDownloads]", source: chrome-extension://ljoplibgfehghmibaoaepfagnmbbfiga/_generated_background_page.html (0)

(as reported in another unrelated  issue 837950  that flakes our tests).

crbug is good at finding these things, _if developer has provided log output_ :)

example https://bugs.chromium.org/p/chromium/issues/list?can=2&q=Error+in+event+handler+for+runtime.onSuspend%3A+TypeError&colspec=ID+Pri+M+Stars+ReleaseBlock+Component+Status+Owner+Summary+OS+Modified&x=m&y=releaseblock&cells=ids