Also failing on Linux:

https://uberchromegw.corp.google.com/i/chromium.linux/builders/Linux%20Tests/builds/66703

alan: would you mind taking a look? Can't seem to find the culprit from the list of CLs. First run where it failed:

https://ci.chromium.org/buildbot/chromium.webkit/WebKit%20Win10/30084

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/20cce4645adf844a80fa798ce854e53edb8455e9

commit 20cce4645adf844a80fa798ce854e53edb8455e9
Author: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Date: Thu Jan 25 04:09:24 2018

sheriff: Disable viewport-unit-transform-responsive.html test

Test keeps timing out on Windows and Linux

TBR=alancutter@chromium.org
NOTRY=true

Bug:  805788 
Change-Id: Id1eeb9a0c6629af693131456dc24a5dce532c211
Reviewed-on: https://chromium-review.googlesource.com/885661
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531809}
[modify] https://crrev.com/20cce4645adf844a80fa798ce854e53edb8455e9/third_party/WebKit/LayoutTests/TestExpectations

This and virtual/threaded/animations/responsive/viewport-unit-translate-responsive.html have started flaking on mac.

I'm suspecting https://chromium-review.googlesource.com/c/chromium/src/+/907501

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8d933fd0dcc4afc837a347fdae72b809c502f6c6

commit 8d933fd0dcc4afc837a347fdae72b809c502f6c6
Author: Kevin McNee <mcnee@chromium.org>
Date: Thu Feb 08 21:30:05 2018

Disable viewport-unit-transform-responsive.html and viewport-unit-translate-responsive.html on Mac

These tests were already flaky on Windows and Linux and now they've
started flaking on Mac.

NOTRY=true
TBR=fsamuel@chromium.org

Bug:  805788 , 805794
Change-Id: I2b655abe10e13f8d458740d3f1d6cb5d1c0e58ce
Reviewed-on: https://chromium-review.googlesource.com/909721
Reviewed-by: Kevin McNee <mcnee@chromium.org>
Reviewed-by: Fady Samuel <fsamuel@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535522}
[modify] https://crrev.com/8d933fd0dcc4afc837a347fdae72b809c502f6c6/third_party/WebKit/LayoutTests/TestExpectations

Thanks for linking the macOS issues in with Window+Linux -- yes, that CL moved macOS to the same path.

This no longer appears to be flaky:

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests&tests=viewport-unit-transform-responsive.html

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests%20(with%20patch)&tests=viewport-unit-transform-responsive.html

I'm going to try re-enabling

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5b941a168d9c7827fe8680e6372cca8ea25896a8

commit 5b941a168d9c7827fe8680e6372cca8ea25896a8
Author: Stephen McGruer <smcgruer@chromium.org>
Date: Mon Jun 11 15:17:33 2018

Re-enable two animations test that no longer appear to be flaky

This is a speculative re-enabling based on the testharness dashboard
appearing green for both these tests.

Bug: 805794,  805788 
Change-Id: Ibfe69c9882a8ec1534329fe568b846d8c1cf8750
Reviewed-on: https://chromium-review.googlesource.com/1094979
Reviewed-by: Yi Gu <yigu@chromium.org>
Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566003}
[modify] https://crrev.com/5b941a168d9c7827fe8680e6372cca8ea25896a8/third_party/WebKit/LayoutTests/TestExpectations