All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=638004

Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?keys=agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgjraz4goM


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

chromium-rel-mac-hdd

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/9004219946451528880

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


=== Bisection aborted ===
The bisect was aborted because The metric values for the initial "good" and "bad" revisions do not represent a clear regression.
Please contact the the team (see below) if you believe this is in error.

=== Warnings ===
The following warnings were raised by the bisect job:

 * Bisect failed to reproduce the regression with enough confidence.

===== TESTED REVISIONS =====
Revision         Mean     Std Dev  N   Good?
chromium@411587  63.6208  2.53313  18  good
chromium@411613  64.1246  3.45863  18  bad

Bisect job ran on: mac_hdd_perf_bisect
Bug ID: 638004

Test Command: src/tools/perf/run_benchmark -v --browser=release --output-format=chartjson --upload-results --also-run-disabled-tests blink_perf.shadow_dom
Test Metric: ContentReprojection/ContentReprojection
Relative Change: 0.26%
Score: 0

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/mac_hdd_perf_bisect/builds/734
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9004219946451528880


Not what you expected? We'll investigate and get back to you!
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5887930699087872

| 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!

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/9000806079190347712

Kicked nother bisect with a wider range

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

Hi abakalov@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 : Switching from the old (CLD2) to the new (CLD3) language detector.
Author  : abakalov
Commit description:
  
Note:
I ran tools/linux/dump-static-initializers.py on CLD3. It did not find any static initializers.

BUG=624904

Review-Url: https://codereview.chromium.org/2244683002
Cr-Commit-Position: refs/heads/master@{#411677}
Commit  : 5b70d355c174c026f936cb5ef795b4d66c1cc4f5
Date    : Fri Aug 12 16:50:05 2016


===== TESTED REVISIONS =====
Revision         Mean     Std Dev   N   Good?
chromium@411571  63.1866  1.20625   5   good
chromium@411628  62.1072  0.558136  5   good
chromium@411656  61.9492  0.993532  5   good
chromium@411670  64.1081  3.4538    12  good
chromium@411674  67.1673  7.16569   11  good
chromium@411676  68.6011  11.0772   12  good
chromium@411677  74.2848  4.28427   12  bad    <--
chromium@411684  74.4192  0.882127  5   bad

Bisect job ran on: mac_hdd_perf_bisect
Bug ID: 638004

Test Command: src/tools/perf/run_benchmark -v --browser=release --output-format=chartjson --upload-results --also-run-disabled-tests blink_perf.shadow_dom
Test Metric: ContentReprojection/ContentReprojection
Relative Change: 17.78%
Score: 98.0

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/mac_hdd_perf_bisect/builds/808
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9000806079190347712


Not what you expected? We'll investigate and get back to you!
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5207411097337856

| 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!

I think this is a duplicate of the following bug which got closed as "WontFix":
https://bugs.chromium.org/p/chromium/issues/detail?id=638025

Please see the last comment in that bug for why our CL is unlikely to cause the regression.

Agreed with #7.

hayato: should we increase the threshold for this benchmark? Even 20-30% regressions turn out not to be real performance issues. Have we caught real regressions with it recently?