All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=634119

Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?keys=agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg5oOvqwkM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg5oPlowkM


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

chromium-rel-win7-gpu-ati
chromium-rel-win7-gpu-intel

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/9005317207856964400

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

Hi jbauman@chromium.org, the bisect results pointed to your CL below as possibly
causing a regression. Please have a look at this info and see whether
your CL be related.


===== BISECT JOB RESULTS =====
Status: completed


===== SUSPECTED CL(s) =====
Subject : Update vsync override in PostSubBuffers.
Author  : jbauman
Commit description:
  
This was only happening in SwapBuffers, so the vsync override could
become stale if only PostSubBuffers were happening.

BUG= 632785 

Review-Url: https://codereview.chromium.org/2188063002
Cr-Commit-Position: refs/heads/master@{#409376}
Commit  : cb571e2230c90eec7d7c498f6dfd293eaa350001
Date    : Tue Aug 02 23:22:01 2016


===== TESTED REVISIONS =====
Revision         Mean     Std Dev  N  Good?
chromium@409358  322.879  4.30428  5  good
chromium@409370  325.234  13.0575  5  good
chromium@409373  316.692  10.8481  5  good
chromium@409375  316.0    11.0682  5  good
chromium@409376  443.71   43.9973  5  bad    <--
chromium@409381  447.93   24.0087  5  bad
chromium@409404  437.688  17.9031  5  bad

Bisect job ran on: winx64intel_perf_bisect
Bug ID: 634119

Test Command: src/tools/perf/run_benchmark -v --browser=release_x64 --output-format=chartjson --upload-results --also-run-disabled-tests media.tough_video_cases_extra
Test Metric: seek/tulip2.mp4_seek_cold
Relative Change: 35.56%
Score: 99.5

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/winx64intel_perf_bisect/builds/1094
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9005317207856964400


Not what you expected? We'll investigate and get back to you!
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5790627057369088

| O O | Visit http://www.chromium.org/developers/speed-infra/perf-bug-faq
|  X  | for more information addressing perf regression bugs. For feedback,
| / \ | file a bug with component Tests>AutoBisect.  Thank you!

Hello,

I just took a look, and the test still seems to be failing.

Did you have a chance to look at this? Do you have any idea if the change bisect identified may really be the root cause of the perf regression?

Thanks!

I can't reproduce this on my system, but it's not too surprising that it's slower. By chance the browser window had been in a weird configuration where vsync was disabled. Even before the fix vsync would be enabled as soon as the window was ever resized, but these tests never do that. Once vsync is enabled rendering won't be as jittery, but some operations get a bit slower because it periodically has to wait for vsync.

This is a tradeoff we've decided we're willing to make, and there's not much we can do to improve it, so marking as WontFix.