All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=759559

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=49c3d107a8f028233b60dbec2fbdc7f6ec76d6dc52fb7480aafd2b6bac715998


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

chromium-rel-mac11-pro

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/8970010522284289440

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

Suspected Commit
  Author : Sahel Sharify
  Commit : f53825a1fb92e74b9a889b9501243e03de57094d
  Date   : Fri Aug 25 19:16:21 2017
  Subject: Wheel scroll latching and async wheel events flags enabled in testing config.

Bisect Details
  Configuration: mac_pro_perf_bisect
  Benchmark    : smoothness.top_25_smooth
  Metric       : first_gesture_scroll_update_latency/http___techcrunch.com
  Change       : 633.04% | 2.261 -> 16.574

Revision             Result                  N
chromium@497451      2.261 +- 1.94292        6      good
chromium@497478      2.20583 +- 2.15357      6      good
chromium@497482      2.10717 +- 1.8277       6      good
chromium@497483      16.7438 +- 4.81641      6      bad       <--
chromium@497484      14.2015 +- 7.57094      6      bad
chromium@497485      16.7967 +- 1.76329      6      bad
chromium@497491      16.3063 +- 5.68881      6      bad
chromium@497504      16.6143 +- 2.99135      6      bad
chromium@497557      16.574 +- 2.84538       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=http...techcrunch.com smoothness.top_25_smooth

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

Debug information about this bisect:
  https://chromeperf.appspot.com/buildbucket_job_status/8970010522284289440


For feedback, file a bug with component Speed>Bisection

2ms for the first_gesture_scroll_update_latency is not a valid number,
This used to be so low since the first synthetic wheel event on mac was sent with zero delta.
https://chromium-review.googlesource.com/656088 changes smoothScrollBy with wheel to be similar to touch and doesn't send a wheel event with zero delta.
The new value (16ms) is the real fist_gesture_scroll_update_latency and it is closer to other platforms (15.26ms on win10 and 51.24ms on linux).