The culprit is probably in https://chromium.googlesource.com/chromium/src/+log/03d7e78c7bbe8a6e52e04fb01cb765341c99626e%5E..9971f5575093b31d6eb537b74c1d63708215ec20?pretty=fuller&n=

Findit identified https://chromium-review.googlesource.com/c/chromium/src/+/1152815
I will revert

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/32eb332bd65c33bd75ace92ef74fca5ad421b21d

commit 32eb332bd65c33bd75ace92ef74fca5ad421b21d
Author: Christos Froussios <cfroussios@chromium.org>
Date: Wed Aug 01 14:53:34 2018

Revert "[blink] Add a time limit to message processing in MessagePort"

This reverts commit 9971f5575093b31d6eb537b74c1d63708215ec20.

Reason for revert: Findit identified this as the culprit of crbug.com/869868
It breaks webexposed/global-interface-listing-shared-worker.html on
Linux and Mac

Original change's description:
> [blink] Add a time limit to message processing in MessagePort
> 
> In addition to existing limit of 200 messages in a single task also
> limit it to 10 milliseconds to avoid starvation.
> 
> This logic will be removed when message-per-task mojo dispatching
> will be implemented.
> 
> BUG=867133
> R=​mek@chromium.org
> 
> Change-Id: I397d60d06e62507e8a322ee9e68be36093fefa57
> Reviewed-on: https://chromium-review.googlesource.com/1152815
> Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
> Commit-Queue: Alexander Timin <altimin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#579751}

TBR=mek@chromium.org,altimin@chromium.org

Change-Id: Id7f61009e4e944ec675d5ff9aa44b713dbfe902e
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 867133, 869868
Reviewed-on: https://chromium-review.googlesource.com/1158745
Reviewed-by: Christos Froussios <cfroussios@chromium.org>
Commit-Queue: Christos Froussios <cfroussios@chromium.org>
Cr-Commit-Position: refs/heads/master@{#579801}
[modify] https://crrev.com/32eb332bd65c33bd75ace92ef74fca5ad421b21d/third_party/blink/renderer/core/messaging/message_port.cc
[modify] https://crrev.com/32eb332bd65c33bd75ace92ef74fca5ad421b21d/third_party/blink/renderer/core/messaging/message_port.h

Assigning altimin@ as their CL got reverted, dropping sheriff label as it doesn't need to be monitored since revert.