Example log:
[ RUN      ] LocaleMacTest.formatTime
../../third_party/WebKit/Source/platform/text/LocaleMacTest.cpp:235: Failure
Expected equality of these values:
  "\xD9\xA1:\xD9\xA2\xD9\xA3 \xD9\x85"
  FormatTime("ar", 13, 23, 00, 000, true).Utf8().data()
    Which is: "\xD9\xA1:\xD9\xA2\xD9\xA3\xC2\xA0\xD9\x85"
../../third_party/WebKit/Source/platform/text/LocaleMacTest.cpp:246: Failure
Expected equality of these values:
  "\xD9\xA1\xD9\xA2:\xD9\xA0\xD9\xA0 \xD8\xB5"
  FormatTime("ar", 00, 00, 00, 000, true).Utf8().data()
    Which is: "\xD9\xA1\xD9\xA2:\xD9\xA0\xD9\xA0\xC2\xA0\xD8\xB5"
../../third_party/WebKit/Source/platform/text/LocaleMacTest.cpp:259: Failure
Expected equality of these values:
  "\xD9\xA7:\xD9\xA0\xD9\xA7:" "\xD9\xA0\xD9\xA7\xD9\xAB\xD9\xA0\xD9\xA0\xD9\xA7 \xD8\xB5"
    Which is: "\xD9\xA7:\xD9\xA0\xD9\xA7:\xD9\xA0\xD9\xA7\xD9\xAB\xD9\xA0\xD9\xA0\xD9\xA7 \xD8\xB5"
  FormatTime("ar", 07, 07, 07, 007, false).Utf8().data()
    Which is: "\xD9\xA7:\xD9\xA0\xD9\xA7:\xD9\xA0\xD9\xA7\xD9\xAB\xD9\xA0\xD9\xA0\xD9\xA7\xC2\xA0\xD8\xB5"
[  FAILED  ] LocaleMacTest.formatTime (19 ms)

So instead of a regular space, we sometimes get \xC2\xA0 which is a "non-breaking space".

Looks like the failing shards are all on Mac-10.13, while passing ones are on Mac-10.9.

Example passing:
https://chromium-swarm.appspot.com/task?id=3ba72c3b2ac5f510&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=3ba72aea0ea5b810&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=3ba728d03201fa10&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=3ba7294524526110&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=3ba73cd0d2f40110&refresh=10&show_raw=1

Example failing:
https://chromium-swarm.appspot.com/task?id=3ba6f10df1cc1910&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=3ba6224beaf6e210&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=3ba46cde7f004510&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=3b94ae1358ec9410&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=3b94acd6cd90b310&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=3b90db053991f710&refresh=10&show_raw=1
https://chromium-swarm.appspot.com/task?id=3b8bc87eb38b1d10&refresh=10&show_raw=1

Over to ellyjones who handled other Mac 10.13 breakages.

One step back: Do you know what's up with this whole situation of having some 10.13 bots in the fleet which fail a bunch of tests, making the tests look flaky? This seems like a pretty bad state to be in; for the average developer (or sheriff) it's hard to figure out what's going on...

Detected 4 new flakes for test/step "LocaleMacTest.formatTime". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNyIwsSBUZsYWtlIhhMb2NhbGVNYWNUZXN0LmZvcm1hdFRpbWUM. This message was posted automatically by the chromium-try-flakes app. Since flakiness is ongoing, the issue was moved back into Sheriff Bug Queue (unless already there).

Flakes keep rolling in. Stand by for CL to disable this test.

CL is here, blocked on (unrelated) closed tree
https://chromium-review.googlesource.com/c/chromium/src/+/922961

Which MacOS settings choosing U+00A0 or U+0020?
We may want to check such settings and use U+00A0 or U+0020 for test expectation.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a79fb8fad0162d42240ba798bb142640ec546486

commit a79fb8fad0162d42240ba798bb142640ec546486
Author: chcunningham <chcunningham@chromium.org>
Date: Fri Feb 16 02:35:01 2018

Disable flaky LocaleMacTest.formatTime

Several flakes over last few days. Potentially related to some
difference in Mac 10.13. Disabling while owners investigate.

Bug:  811685 
Change-Id: Ided6dafc0f9589af9434a076bdcdcebd72d98b48
TBR: ellyjones@chromium.org,tkent@chromium.org,yosin@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/922961
Reviewed-by: Chrome Cunningham <chcunningham@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Chrome Cunningham <chcunningham@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537120}
[modify] https://crrev.com/a79fb8fad0162d42240ba798bb142640ec546486/third_party/WebKit/Source/platform/text/LocaleMacTest.cpp

Detected 5 new flakes for test/step "LocaleMacTest.formatTime". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNyIwsSBUZsYWtlIhhMb2NhbGVNYWNUZXN0LmZvcm1hdFRpbWUM. This message was posted automatically by the chromium-try-flakes app. Since flakiness is ongoing, the issue was moved back into Sheriff Bug Queue (unless already there).

It looks like comment #10 and #11 overlapped. i.e. #11 is talking about stuff that happened before #10 landed. Removing Sheriff-Chromium.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e0bd3176761fcbbd6a0f7063c0c922b723ced745

commit e0bd3176761fcbbd6a0f7063c0c922b723ced745
Author: Elly Fong-Jones <ellyjones@chromium.org>
Date: Tue Oct 16 19:19:56 2018

blink: support macos 10.13+ Arabic date formatting

On MacOS 10.13+, NSDateFormatter formats Arabic dates using non-breaking spaces
instead of ascii spaces. This behavior is probably more correct but there's no
way to configure pre-10.13 NSDateFormatters to behave that way as well, so this
change simply has LocaleMacTest.formatTime test for the behavior per OS version.

This re-enables LocaleMacTest.formatTime.

Bug:  811685 
Change-Id: Ib25247a28f382639d9aadde45fb1db01aff1c2d8
Reviewed-on: https://chromium-review.googlesource.com/c/1283834
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600075}
[modify] https://crrev.com/e0bd3176761fcbbd6a0f7063c0c922b723ced745/third_party/blink/renderer/platform/text/DEPS
[modify] https://crrev.com/e0bd3176761fcbbd6a0f7063c0c922b723ced745/third_party/blink/renderer/platform/text/locale_mac_test.cc