I don't have enough context regarding the migration ( issue 818301 ). Is https://crrev.com/c/999129 meant to be transient or permanent? If it's permanent, is the fix simply changing the tester of mac10.12_blink_rel to Mac10.13 Tests? (I'm a bit confused because the CL has a TODO under Mac10.13 Tests saying "Switch this to 10.13"; when that happens, which builder runs layout tests on 10.12?)

tandrii@ is migrating mac_chromium_rel_ng from buildbot to LUCI. In doing so, he's also migrating the mirrored CI bots. One of those is a chromium.webkit bot, though, and we don't want those to be migrated. https://crrev.com/c/999129 was solely intended to move the tests from the mirrored chromium.webkit bot onto a bot that will continue to be mirrored by mac_chromium_rel_ng s.t. we didn't lose mac layout test coverage on the CQ.

Running them on that bot on 10.12 is temporary; we plan to move them to 10.13, like the rest of the tests on that bot.

The permanent home for layout tests on 10.12 should be chromium.mac:Mac10.12 Tests and its mirrored try bot, mac_chromium_10.12_rel_ng. mac10.12_blink_rel, like WebKit Mac10.12, should be removed entirely.

Thanks for the context, John. Yeah that plan makes sense.

So I guess along with chromium.webkit, all *_blink_rel trybots should be turned down as well. And rebaseline will switch to the corresponding bots on chromium.{mac,win,linux}.

Let me try to switch from mac10.12_blink_rel to mac_chromium_10.12_rel_ng in webkitpy and see if it works :)

Assigning to  robertma@ to determine if any further action needed here.

 Issue 831036  has been merged into this issue.

For anyone whose CL is blocked by this bug, here is the workaround (copied from  bug 831036 ):

1. Open the layout test result page on mac_chromium_rel_ng;
2. Select "Rebaseline script" format, and copy report;
3. In local directory LayoutTests/platform/mac-mac10.12, <paste>
4. In the test result page, click "Copy single line"
5. webkit-patch optimize-baselines <paste>

Fix underway:
https://chromium-review.googlesource.com/c/chromium/src/+/1003132

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/856f6a9085a89eac72d587caafe17053f02e0390

commit 856f6a9085a89eac72d587caafe17053f02e0390
Author: Robert Ma <robertma@chromium.org>
Date: Tue Apr 10 23:30:18 2018

[webkitpy] Migrate to Buildbucket and switch to a new Mac try bot

The immediate issue this CL tries to fix is  crbug.com/830629 , which is
fixed by using mac_chromium_rel_ng instead of mac10.12_blink_rel for
rebaselining on Mac 10.12. After  crbug.com/818301 , the remaining
*_blink_rel bots need to be replaced as well.

(NOTE: mac_chromium_rel_ng is planned to be upgraded to 10.13 soon.
When that happens, mac_chromium_10.12_rel_ng should be used for 10.12.
We are using mac_chromium_rel_ng for now only because of capacity
issues of mac_chromium_10.12_rel_ng.)

Meanwhile, we take this chance to add support for LUCI Buildbucket as
Buildbot (and its "master" concept) is being deprecated. Buildbuckets
for each bot can now be specified in builders.json. The special
treatment for android_blink_rel is also moved into builders.json to
reduce the amount of magic in the code.

Bug:  830629 
Change-Id: I4c1777f93ff63ccd7bc35abaaea435eafd19e18c
Reviewed-on: https://chromium-review.googlesource.com/1003132
Commit-Queue: Robert Ma <robertma@chromium.org>
Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549676}
[modify] https://crrev.com/856f6a9085a89eac72d587caafe17053f02e0390/third_party/WebKit/Tools/Scripts/webkitpy/common/config/builders.json
[modify] https://crrev.com/856f6a9085a89eac72d587caafe17053f02e0390/third_party/WebKit/Tools/Scripts/webkitpy/common/host_mock.py
[modify] https://crrev.com/856f6a9085a89eac72d587caafe17053f02e0390/third_party/WebKit/Tools/Scripts/webkitpy/common/net/git_cl.py
[modify] https://crrev.com/856f6a9085a89eac72d587caafe17053f02e0390/third_party/WebKit/Tools/Scripts/webkitpy/common/net/git_cl_mock.py
[modify] https://crrev.com/856f6a9085a89eac72d587caafe17053f02e0390/third_party/WebKit/Tools/Scripts/webkitpy/common/net/git_cl_unittest.py
[modify] https://crrev.com/856f6a9085a89eac72d587caafe17053f02e0390/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/builder_list.py
[modify] https://crrev.com/856f6a9085a89eac72d587caafe17053f02e0390/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/builder_list_unittest.py
[modify] https://crrev.com/856f6a9085a89eac72d587caafe17053f02e0390/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/try_flag.py
[modify] https://crrev.com/856f6a9085a89eac72d587caafe17053f02e0390/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/try_flag_unittest.py
[modify] https://crrev.com/856f6a9085a89eac72d587caafe17053f02e0390/third_party/WebKit/Tools/Scripts/webkitpy/tool/commands/rebaseline_cl_unittest.py

Fixed by switching to mac_chromium_rel_ng