All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=634917

Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?keys=agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICgpuajuwsM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg5rCF6goM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICg5oTRuwoM,agxzfmNocm9tZXBlcmZyFAsSB0Fub21hbHkYgICglsj8qAoM


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

chromium-rel-mac-hdd
chromium-rel-mac-retina
chromium-rel-mac10
chromium-rel-mac11

Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/9005160320731443728

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

Hi rsesek@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 : [Mac] Only enable the CFBundleBlocker in the browser process.
Author  : rsesek
Commit description:
  
In child processes, which are sandboxed in most cases, the sandbox will prevent
access to the filesystem locations where the potentially blocked bundles are
stored. Furthermore, on macOS 10.11 and higher, the Google Chrome build is
codesigned in such a way where bundle loading is blocked by SIP.

This reduces some of the "triggered DYLD shared region unnest for map" messages.

BUG= 428858 
R=mark@chromium.org

Review-Url: https://codereview.chromium.org/2199313002
Cr-Commit-Position: refs/heads/master@{#409244}
Commit  : 65e732d3b4dc595512b731143fd49d372acc1a87
Date    : Tue Aug 02 18:15:45 2016


===== TESTED REVISIONS =====
Revision         Mean     Std Dev  N  Good?
chromium@409230  487.747  10.0112  5  good
chromium@409238  500.566  27.2385  8  good
chromium@409242  498.691  10.5482  8  good
chromium@409243  493.092  14.1985  8  good
chromium@409244  514.395  9.12625  8  bad    <--
chromium@409246  510.961  9.07768  8  bad

Bisect job ran on: mac_hdd_perf_bisect
Bug ID: 634917

Test Command: src/tools/perf/run_benchmark -v --browser=release --output-format=chartjson --upload-results --also-run-disabled-tests startup.warm.blank_page
Test Metric: open_tabs_time/open_tabs_time
Relative Change: 4.92%
Score: 99.0

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/mac_hdd_perf_bisect/builds/709
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9005160320731443728


Not what you expected? We'll investigate and get back to you!
  https://chromeperf.appspot.com/bad_bisect?try_job_id=5878870750789632

| 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 find this rather surprising, though perhaps we are eliminating some IO and mutex acquisition in our overrided CFBundle.

Mark: Should we just revert the CL?

That’s weird. I guess I’d have to agree with your “perhaps” from comment 4.

Try backing it out to confirm that we recover the loss first. If we can confirm this as a cause, then I guess we can brainstorm over ☕️.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3026ec1f3bd67bb2cac5e42fe6d1a1298efcd049

commit 3026ec1f3bd67bb2cac5e42fe6d1a1298efcd049
Author: rsesek <rsesek@chromium.org>
Date: Fri Aug 05 18:21:19 2016

Revert of [Mac] Only enable the CFBundleBlocker in the browser process. (patchset #1 id:1 of https://codereview.chromium.org/2199313002/ )

Reason for revert:
Speculative revert for perf regression.

BUG= https://crbug.com/634917 

Original issue's description:
> [Mac] Only enable the CFBundleBlocker in the browser process.
>
> In child processes, which are sandboxed in most cases, the sandbox will prevent
> access to the filesystem locations where the potentially blocked bundles are
> stored. Furthermore, on macOS 10.11 and higher, the Google Chrome build is
> codesigned in such a way where bundle loading is blocked by SIP.
>
> This reduces some of the "triggered DYLD shared region unnest for map" messages.
>
> BUG= 428858 
> R=mark@chromium.org
>
> Committed: https://crrev.com/65e732d3b4dc595512b731143fd49d372acc1a87
> Cr-Commit-Position: refs/heads/master@{#409244}

TBR=mark@chromium.org,thakis@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG= 428858 

Review-Url: https://codereview.chromium.org/2218163002
Cr-Commit-Position: refs/heads/master@{#410113}

[modify] https://crrev.com/3026ec1f3bd67bb2cac5e42fe6d1a1298efcd049/chrome/app/chrome_main_delegate.cc

That did seem to do it. Oh well.