Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/8975555914703948704

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

Hi ulan@chromium.org, the bisect results pointed to your CL, please take a look at the
results.


=== BISECT JOB RESULTS ===
Perf regression found with culprit

Suspected Commit
  Author : Ulan Degenbaev
  Commit : 5d8840e24e0e98136c081ee22441d808412d06e2
  Date   : Thu Jun 22 12:37:26 2017
  Subject: [runtime] Copy descriptors on prototype map transition.

Bisect Details
  Configuration: winx64_high_dpi_perf_bisect
  Benchmark    : v8.browsing_desktop
  Metric       : memory:chrome:renderer_processes:reported_by_chrome:v8:heap:allocated_objects_size_max/browse_social/browse_social_twitter
  Change       : 31.45% | 48828146.6667 -> 64184816.0

Revision                           Result                    N
chromium@481508                    48828147 +- 4085528       6      good
chromium@481559                    46629512 +- 12090742      6      good
chromium@481584                    47834695 +- 7282590       6      good
chromium@481586                    47642404 +- 6818434       6      good
chromium@481586,v8@6681949808      46573955 +- 4024827       6      good
chromium@481586,v8@79ec067252      48482203 +- 3303665       6      good
chromium@481586,v8@5d8840e24e      63628983 +- 4588712       6      bad       <--
chromium@481587                    64456239 +- 5442563       6      bad
chromium@481588                    64126963 +- 5167360       6      bad
chromium@481591                    61806772 +- 3738071       6      bad
chromium@481597                    63439603 +- 3136565       6      bad
chromium@481609                    64184816 +- 2305075       6      bad

To Run This Test
  src/tools/perf/run_benchmark -v --browser=release_x64 --output-format=chartjson --upload-results --pageset-repeat=1 --also-run-disabled-tests --story-filter=browse.social.twitter v8.browsing_desktop

Debug Info
  https://chromeperf.appspot.com/buildbucket_job_status/8975555914703948704

Is this bisect wrong?
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5336527900508160


| 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 Speed>Bisection.  Thank you!

 Issue 737473  has been merged into this issue.

 Issue 736686  has been merged into this issue.

Issue 738837 has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/973314f2e1d00831dd525e2214aacf5fb6c86ecb

commit 973314f2e1d00831dd525e2214aacf5fb6c86ecb
Author: Ulan Degenbaev <ulan@chromium.org>
Date: Tue Jul 18 18:03:19 2017

Revert "[runtime] Copy descriptors on prototype map transition."

This reverts commit 5d8840e24e0e98136c081ee22441d808412d06e2.

Reason for revert: performance regressions.

BUG= chromium:737472 ,chromium:736640

Original change's description:
> [runtime] Copy descriptors on prototype map transition.
> 
> Currently the descriptors are moved from the old map to the new map,
> which is unsafe for the concurrent marker. This patch removes the map
> mutation.
> 
> Change-Id: I3f7ce455c7344148a122c7443cf32a4eef0307be
> Reviewed-on: https://chromium-review.googlesource.com/535480
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#46131}

TBR=ulan@chromium.org,verwaest@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I2525a8101a01f39ccad1a6e49aae1e3f28da5b5d
Reviewed-on: https://chromium-review.googlesource.com/555551
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46745}
[modify] https://crrev.com/973314f2e1d00831dd525e2214aacf5fb6c86ecb/src/objects.cc

The culprit CL was reverted.

 Issue 736647  has been merged into this issue.