All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=771691

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=6383e5e053c037bd2ce5f9f3630b53114fc4b299fcdd13770c3fe213c987e02b


Bot(s) for this bug's original alert(s):

linux-release

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/8966642635698708096

=== Auto-CCing suspected CL author kojii@chromium.org ===

Hi kojii@chromium.org, the bisect results pointed to your CL, please take a look at the
results.


=== BISECT JOB RESULTS ===
Perf regression found with culprit

Suspected Commit
  Author : Koji Ishii
  Commit : 6541835c4e9db26be7685581b1f263cf9a3f17c0
  Date   : Thu Sep 28 05:00:27 2017
  Subject: [LayoutNG] Add LayoutNGListItem for 'display: list-item'

Bisect Details
  Configuration: linux_perf_bisect
  Benchmark    : speedometer2
  Metric       : Inferno-TodoMVC/Speedometer2
  Change       : 3.75% | 760.122 -> 788.58875

Revision             Result                  N
chromium@504827      760.122 +- 13.7312      6      good
chromium@504899      753.594 +- 9.01153      6      good
chromium@504908      759.845 +- 6.49182      6      good
chromium@504909      787.213 +- 16.2651      6      bad       <--
chromium@504910      790.257 +- 9.36644      6      bad
chromium@504911      793.527 +- 19.4359      6      bad
chromium@504913      790.86 +- 19.45         6      bad
chromium@504917      784.982 +- 9.44664      6      bad
chromium@504935      786.163 +- 15.7738      6      bad
chromium@504971      788.589 +- 9.61837      6      bad

To Run This Test
  src/tools/perf/run_benchmark -v --browser=release --output-format=chartjson --upload-results --pageset-repeat=1 --also-run-disabled-tests --story-filter=Speedometer2 speedometer2

More information on addressing performance regressions:
  http://g.co/ChromePerformanceRegressions

Debug information about this bisect:
  https://chromeperf.appspot.com/buildbucket_job_status/8966642635698708096


For feedback, file a bug with component Speed>Bisection

Re-reviewed the patch, the CL adds a runtime flag check for LayoutNG, and no additional code runs unless it's enabled. I don't think there's much we can do, and it'll be gone once we make a switch to LayoutNG.