Looking at the codebase/history, perhaps we need to apply the same treatment in https://chromium-review.googlesource.com/c/chromium/src/+/1103846 to mac10.12-blink-rel, too?

I'll take a look. I was pretty sure I had tested this ...

 Issue 854227  has been merged into this issue.

Re #2: it was working when you first landed the change, but then suddenly we no longer had bots with no GPU

We must've moved all of the VMs (gpu:none) into the Chrome-quarantine pool, leaving these orphaned. Fixing now.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/97f97ae63b2b672c08929e99c7cbe53fe1127cd3

commit 97f97ae63b2b672c08929e99c7cbe53fe1127cd3
Author: Dirk Pranke <dpranke@chromium.org>
Date: Tue Jun 19 22:22:36 2018

Update swarming dimensions for tryserver.blink.

The mac10.12-blink-rel bot has no machines that can run its tasks.
To fix this, and to be explicit about the other configurations needed,
this CL makes the swarming dimensions explicitly specified for those
mac builders.

TBR=robertma@chromium.org
BUG= 854039 

Change-Id: Id4e79d9c0f47f36fd258769cfcc5f39b8c12e677
Reviewed-on: https://chromium-review.googlesource.com/1106613
Reviewed-by: Robert Ma <robertma@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568618}
[modify] https://crrev.com/97f97ae63b2b672c08929e99c7cbe53fe1127cd3/testing/buildbot/chromium.fyi.json
[modify] https://crrev.com/97f97ae63b2b672c08929e99c7cbe53fe1127cd3/testing/buildbot/test_suite_exceptions.pyl
[modify] https://crrev.com/97f97ae63b2b672c08929e99c7cbe53fe1127cd3/testing/buildbot/waterfalls.pyl

This should be fixed now.