All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=639383

Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?keys=agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgzu7NvwoM


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

chromium-rel-win7-gpu-ati

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/9003875897063680160

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

Hi dominicc@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 : Expose CustomElementsRegistry as an experimental web platform feature.
Author  : dominicc
Commit description:
  
BUG= 594918 

Review-Url: https://codereview.chromium.org/2247633003
Cr-Commit-Position: refs/heads/master@{#411971}
Commit  : bd6470a3994c772c9d34be522e024013ca6b8649
Date    : Mon Aug 15 16:03:52 2016


===== TESTED REVISIONS =====
Revision         Mean     Std Dev  N   Good?
chromium@411965  800.266  37.5698  12  good
chromium@411969  755.422  56.5831  27  good
chromium@411970  756.458  61.673   27  good
chromium@411971  697.288  54.9958  18  bad    <--
chromium@411972  678.486  60.9475  12  bad
chromium@411978  693.405  54.0452  8   bad
chromium@411990  702.071  48.5526  8   bad

Bisect job ran on: winx64ati_perf_bisect
Bug ID: 639383

Test Command: src/tools/perf/run_benchmark -v --browser=release_x64 --output-format=chartjson --upload-results --also-run-disabled-tests blink_perf.bindings
Test Metric: create-element/create-element
Relative Change: 9.64%
Score: 99.8

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/winx64ati_perf_bisect/builds/1516
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9003875897063680160


Not what you expected? We'll investigate and get back to you!
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5284894138171392

| 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!

Patch up at https://codereview.chromium.org/2288653002

Here's a perf tryjob for the patch which shows 10.5% improvement; I think this should be enough? Custom elements does entail more work in createElement.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a67c4b53027ee270f17241d7a594ac10aef33790

commit a67c4b53027ee270f17241d7a594ac10aef33790
Author: dominicc <dominicc@chromium.org>
Date: Wed Sep 07 16:36:58 2016

Make custom element name checks faster and fewer

This makes some changes to make things faster, suggested by esprehn
in  Issue 631931  and discussion:

- Weakens some CHECKs that custom elements should be created to DCHECKs.
- Specializes 8-bit strings.
- Does a quick reject for names without hyphens.
- Does one fewer name checks in the createElement case.

BUG= 631931 , 639383 

Review-Url: https://codereview.chromium.org/2288653002
Cr-Commit-Position: refs/heads/master@{#416959}

[modify] https://crrev.com/a67c4b53027ee270f17241d7a594ac10aef33790/third_party/WebKit/Source/build/scripts/templates/ElementFactory.cpp.tmpl
[modify] https://crrev.com/a67c4b53027ee270f17241d7a594ac10aef33790/third_party/WebKit/Source/core/dom/custom/CustomElement.cpp
[modify] https://crrev.com/a67c4b53027ee270f17241d7a594ac10aef33790/third_party/WebKit/Source/core/dom/custom/CustomElement.h
[modify] https://crrev.com/a67c4b53027ee270f17241d7a594ac10aef33790/third_party/WebKit/Source/core/dom/custom/CustomElementTest.cpp
[modify] https://crrev.com/a67c4b53027ee270f17241d7a594ac10aef33790/third_party/WebKit/Source/platform/text/Character.h

Graphs improved; I believe this is OK now but please sanity check me. Note the reference builds are appreciably lower after r416453.