Yes this just stopped my CL passing CQ too.

The flakiness dashboard shows this test frequently only passes on retry:

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests&tests=timeline-usertiming.js

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e27128fba83040c35442ba4fde309015a0b595bc

commit e27128fba83040c35442ba4fde309015a0b595bc
Author: Andrey Kosyakov <caseq@chromium.org>
Date: Thu May 24 22:58:44 2018

Mark devtools/tracing/timeline-time/timeline-usertiming.js as flaky

Drive-by: merge entries for timeline-recalculate-styles.js

TBR: alph@chromium.org, jam@chromium.org
Bug:  823837 
Change-Id: I8d29104d3784747bfb5260c8349d409dc7d016f5
Reviewed-on: https://chromium-review.googlesource.com/1072413
Commit-Queue: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561673}
[modify] https://crrev.com/e27128fba83040c35442ba4fde309015a0b595bc/third_party/WebKit/LayoutTests/TestExpectations

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1eda4c22b63a714e90ca8594ca796598eb1307c7

commit 1eda4c22b63a714e90ca8594ca796598eb1307c7
Author: Alexei Filippov <alph@chromium.org>
Date: Sat May 26 02:55:27 2018

DevTools: Do not sort async events by endTime.

We used to sort async events having the same start time by end time.
That added a non-deterministic behavior causing some events being swapped
if their start time accidentally happens to be the same.

BUG= 823837 

Change-Id: I6068da8f8c9d2b7a0730003b19bf37fb2d3af590
Reviewed-on: https://chromium-review.googlesource.com/1073612
Commit-Queue: Alexei Filippov <alph@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#562109}
[modify] https://crrev.com/1eda4c22b63a714e90ca8594ca796598eb1307c7/third_party/WebKit/LayoutTests/TestExpectations
[modify] https://crrev.com/1eda4c22b63a714e90ca8594ca796598eb1307c7/third_party/WebKit/LayoutTests/http/tests/devtools/tracing/timeline-time/timeline-usertiming-expected.txt
[modify] https://crrev.com/1eda4c22b63a714e90ca8594ca796598eb1307c7/third_party/WebKit/LayoutTests/http/tests/devtools/tracing/timeline-time/timeline-usertiming.js
[modify] https://crrev.com/1eda4c22b63a714e90ca8594ca796598eb1307c7/third_party/WebKit/LayoutTests/http/tests/devtools/tracing/trace-event-self-time-expected.txt
[modify] https://crrev.com/1eda4c22b63a714e90ca8594ca796598eb1307c7/third_party/blink/renderer/devtools/front_end/sdk/TracingModel.js
[modify] https://crrev.com/1eda4c22b63a714e90ca8594ca796598eb1307c7/third_party/blink/renderer/devtools/front_end/timeline_model/TimelineModel.js