All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=756876

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=7ec826a5c73e7e9ff14c0836055ee4289462109fc1a5a881baebe12a7c97e19c


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

chromium-rel-win8-dual

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/8970907679855771920

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

Hi chaopeng@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 : chaopeng
  Commit : a00842bbcbb75703c1508c462ef7423ead639da1
  Date   : Mon Aug 14 13:49:16 2017
  Subject: Overlay Scrollbar track not block hit test

Bisect Details
  Configuration: win_8_perf_bisect
  Benchmark    : blink_perf.events
  Metric       : hit-test-lots-of-layers/hit-test-lots-of-layers
  Change       : 17.63% | 0.596250798819 -> 0.491126354071

Revision             Result                      N
chromium@494020      0.596251 +- 0.00340711      6      good
chromium@494033      0.59417 +- 0.00290385       6      good
chromium@494039      0.594718 +- 0.00191424      6      good
chromium@494041      0.592798 +- 0.00687119      6      good
chromium@494042      0.490786 +- 0.00418675      6      bad       <--
chromium@494045      0.491126 +- 0.00268682      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 blink_perf.events

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

Debug information about this bisect:
  https://chromeperf.appspot.com/buildbucket_job_status/8970907679855771920


For feedback, file a bug with component Speed>Bisection

The CL is reverted.