The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/85f612d2b2b7dac856e689710015315195f322a5

commit 85f612d2b2b7dac856e689710015315195f322a5
Author: Alexei Filippov <alph@chromium.org>
Date: Tue Mar 27 20:12:56 2018

DevTools: Add aggregated tree for user timing events on timeline.

BUG= 826045 

Change-Id: I7273015bcac131f028116380e928f6a9c6d67182
Reviewed-on: https://chromium-review.googlesource.com/981444
Commit-Queue: Alexei Filippov <alph@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546226}
[add] https://crrev.com/85f612d2b2b7dac856e689710015315195f322a5/third_party/WebKit/LayoutTests/http/tests/devtools/tracing/timeline-misc/timeline-user-timings-expected.txt
[add] https://crrev.com/85f612d2b2b7dac856e689710015315195f322a5/third_party/WebKit/LayoutTests/http/tests/devtools/tracing/timeline-misc/timeline-user-timings.js
[modify] https://crrev.com/85f612d2b2b7dac856e689710015315195f322a5/third_party/WebKit/Source/devtools/front_end/timeline/TimelineTreeView.js
[modify] https://crrev.com/85f612d2b2b7dac856e689710015315195f322a5/third_party/WebKit/Source/devtools/front_end/timeline_model/TimelineModel.js

Did https://chromium-review.googlesource.com/c/chromium/src/+/976982 revert this? 

I'm not seeing it any longer.

can't repro.

Deleted: Screenshot from 2018-04-04 15-05-07.png 123 KB

	Screenshot from 2018-04-04 15-05-07.png 123 KB View Download

tight. didnt grok the track selection but it makes sense.