All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=846335

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=54b1dc3754fb54a31f5a5b9a1b8b1c143edf1b6f4531d67f0b5c9b86b8a64e3e


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

android-nexus5
android-nexus5X

📍 Pinpoint job started.
https://pinpoint-dot-chromeperf.appspot.com/job/11f58612240000

📍 Found a significant difference after 1 commit.
https://pinpoint-dot-chromeperf.appspot.com/job/11f58612240000

Fix regression in thread_times.key_mobile_sites_smooth by yiyix@chromium.org
https://chromium.googlesource.com/chromium/src/+/be2578711ee47f8b8a5ba8b15108dedb50a27367

Understanding performance regressions:
  http://g.co/ChromePerformanceRegressions

the improvement was due to this cl, https://chromium-review.googlesource.com/c/chromium/src/+/1029733 and it has cause more 20 regression in other metrics. the cl mentioned here, has fixed those regressions and smoothness:sync_scroll.key_mobile_sites_smooth timing is back to the point before the fake improvement. No bug.