All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=754844

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=8cf24e52ab110618007278b0bd89ef557efe57ec8eb940547c36de6baf10d44b


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

win-high-dpi

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/8971524496903951904

=== Auto-CCing suspected CL author robertphillips@google.com ===

Hi robertphillips@google.com, 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 : Robert Phillips
  Commit : 952144753dc31d9d935683123cae43fca483bade
  Date   : Tue Aug 08 22:32:36 2017
  Subject: Add explicit clear of stencil buffer before opLists that use them

Bisect Details
  Configuration: winx64_high_dpi_perf_bisect
  Benchmark    : smoothness.tough_animation_cases
  Metric       : frame_times/css_value_type_shadow.html?api_css_animations_N_0316
  Change       : 20.58% | 59.4417938439 -> 71.6771990329

Revision                             Result                   N
chromium@492693                      59.4418 +- 1.40931       6      good
chromium@492785                      59.9188 +- 4.93126       6      good
chromium@492831                      59.9469 +- 1.94697       6      good
chromium@492854                      61.7023 +- 7.21595       6      good
chromium@492857                      60.7138 +- 10.121        6      good
chromium@492859                      60.1661 +- 11.1907       6      good
chromium@492859,skia@26308e1757      59.3101 +- 2.24048       6      good
chromium@492859,skia@3404207e24      60.2543 +- 1.95671       6      good
chromium@492859,skia@8d8b016f52      58.4915 +- 1.44749       6      good
chromium@492859,skia@952144753d      72.5309 +- 2.0699        6      bad       <--
chromium@492860                      73.4361 +- 0.868758      6      bad
chromium@492866                      72.3286 +- 1.39998       6      bad
chromium@492877                      71.6772 +- 0.647207      6      bad

To Run This Test
  src/tools/perf/run_benchmark -v --browser=release_x64 --output-format=chartjson --upload-results --pageset-repeat=1 --also-run-disabled-tests --story-filter=css.value.type.shadow.html.api.css.animations.N.0316 smoothness.tough_animation_cases

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

Debug information about this bisect:
  https://chromeperf.appspot.com/buildbucket_job_status/8971524496903951904


For feedback, file a bug with component Speed>Bisection

The Skia-side fix for this landed in:

https://skia-review.googlesource.com/c/skia/+/40691 (Reduce stencil buffer clearing)

It rolled into Chrome in:

https://chromium-review.googlesource.com/c/chromium/src/+/644500 (Roll src/third_party/skia/ ad8a43f76..cb2e235e6) 

at 498683. It appears to have fixed the regression on the Chromium perf bots.