All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=631953

Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?keys=agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICghrS9vgkM


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

chromium-rel-win7-gpu-ati

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/9005990421912668720

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

Hi drott@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 : Unify glyph metrics to use the same Skia API
Author  : drott
Commit description:
  
Use identical glyph metrics based bounds in HarfBuzz callbacks as well
as ShapeResult's glyph bounds calculation, except on Mac, due to Skia
bug https://bugs.chromium.org/p/skia/issues/detail?id=5328

* Using the same glyph bounds callback in HarfBuzz shaping and in
  ShapeResult's glyph bounds calculation enables reusing of the same
  cache in Skia, as opposed to using the cached glyph metrics based
  cache vs. using a second cache for path based metrics before.

Local benchmarking of the blink_perf.layout shows 12.44%
improvements for the character_fallback test and 1.8-5%
improvements on chapter-reflow-once, line-layout and
latin-complex-test. There are also some hits on flexbox-lots of
data and flexbox-row-nowrap. I am not 100% convinced that the
local benchmarks are accurate enough and would like to observe
the results on the bot. Overall, we should see a layout speed
improvement, perhaps even in the page cyclers.

BUG= 610313 
R=kojii,tzik

Review-Url: https://codereview.chromium.org/1980913002
Cr-Commit-Position: refs/heads/master@{#407755}
Commit  : 9e47ba024f0061ea667565451c2842f66813fee7
Date    : Tue Jul 26 09:59:36 2016


===== TESTED REVISIONS =====
Revision         Mean     Std Dev   N  Good?
chromium@407731  24.4012  0.110493  5  good
chromium@407743  24.8161  0.101076  5  good
chromium@407750  24.9924  0.056307  5  good
chromium@407753  24.5196  0.378856  5  good
chromium@407754  24.2278  0.127968  5  good
chromium@407755  20.9816  0.198346  5  bad    <--

Bisect job ran on: winx64ati_perf_bisect
Bug ID: 631953

Test Command: src/tools/perf/run_benchmark -v --browser=release_x64 --output-format=chartjson --upload-results --also-run-disabled-tests blink_perf.layout
Test Metric: flexbox-lots-of-data/flexbox-lots-of-data
Relative Change: 14.01%
Score: 99.9

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/winx64ati_perf_bisect/builds/1456
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9005990421912668720


Not what you expected? We'll investigate and get back to you!
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5807915147984896

| 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!

https://codereview.chromium.org/2192483002 hopefully helps with that.

Hi drott@,

I am not seeing recovery on the graphs even after that patch landed, any other ideas?

While the benchmark result for this microbenchmark has dropped, character_fallback from the same set has improved and we're seeing good improvements on Windows page cyclers, which are more important. Also, this CL was the basis for a 300-450k memory saving on Android WebView memory health tests, see issue 577306 - that's why I suggest to accept this trade-off.

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