All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=625897

Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?keys=agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgkpnlrgoM


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

android-one

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

Hi tkent@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 : Improve performance of HTMLSelectElement::m_listItems update.
Author  : tkent
Commit description:
  
This CL introduces a fast path to update m_listItems directly instead of throwing
it away and reconstructing it. The fast path supports:
 - Prepend an OPTION to a SELECT element
 - Append an OPTION to a SELECT element
 - Remove an OPTION child from a SELECT element or an OPTGROUP element.

Removing 20,000 OPTIONs: 2,813ms -> 200ms

BUG= 620142 ,  624220 

Review-Url: https://codereview.chromium.org/2110303002
Cr-Commit-Position: refs/heads/master@{#403093}
Commit  : ef9c38f033c0f5b11defe2210d2d00737c41b76e
Date    : Thu Jun 30 05:28:21 2016


===== TESTED REVISIONS =====
Revision         Mean     Std Dev  N  Good?
chromium@403075  317.712  3.62342  5  good
chromium@403091  317.364  3.1772   5  good
chromium@403092  316.848  6.67326  5  good
chromium@403093  266.159  2.75534  5  bad    <--
chromium@403095  268.551  2.99991  5  bad
chromium@403099  267.53   4.64111  5  bad
chromium@403106  266.686  2.88345  5  bad

Bisect job ran on: android_one_perf_bisect
Bug ID: 625897

Test Command: src/tools/perf/run_benchmark -v --browser=android-chromium --output-format=chartjson --upload-results --also-run-disabled-tests blink_perf.dom
Test Metric: select-single-add/select-single-add
Relative Change: 16.06%
Score: 99.9

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/android_one_perf_bisect/builds/1387
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9007942768019286000


Not what you expected? We'll investigate and get back to you!
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5832249543491584

| 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!

Oh, I found select-single-add was broken since the first checkin.  The test result doesn't make sense.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/48c94c10227b4c93bfbc4cf44081bc633c974043

commit 48c94c10227b4c93bfbc4cf44081bc633c974043
Author: tkent <tkent@chromium.org>
Date: Wed Jul 06 01:35:32 2016

Fix blink_perf.dom select-single-add.html.

The test has never worked as expected.
The intention of the test is to measure the performance to add OPTIONs to a
SELECT element by
 - Adding 250 selected OPTIONs, and
 - Adding 250 unselected OPTIONs.

But it worked expectedly only at the first run. Actually, 499 unselected OPTIONs
and 1 selected OPTION were added after the first run because appendChild()
updates selected state.

This CL makes select-single-add.html slower intentionally.
This CL doesn't affect production.

BUG= 625897 
NOTRY=true

Review-Url: https://codereview.chromium.org/2119413002
Cr-Commit-Position: refs/heads/master@{#403835}

[modify] https://crrev.com/48c94c10227b4c93bfbc4cf44081bc633c974043/third_party/WebKit/PerformanceTests/DOM/select-single-add.html

The test was broken, and should be slower :(