So the idea here is to avoid having to click "Capture Specifics" in chrome://sync-internals, and/or in order to start capturing very early after startup?

My use case is to avoid clicking.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b741423b44b8aa7ac5b1ab274ed8f77c3571a623

commit b741423b44b8aa7ac5b1ab274ed8f77c3571a623
Author: David Davidović <davidovic@google.com>
Date: Wed Jul 25 12:16:14 2018

[sync::consent::cleanup] Inject Clock for testing

When testing the recording of Gaia consents by ConsentAuditor, instead
of relying on the current wall-clock time to check if the consent time
was recorded correctly, inject a fake clock set to a hardcoded date &
time instead.

Bug:  859878 
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I86354fcfdd22e6e4147d1b056a0ffdef377a30e1
Reviewed-on: https://chromium-review.googlesource.com/1146803
Reviewed-by: vitaliii <vitaliii@chromium.org>
Commit-Queue: David Davidović <davidovic@google.com>
Cr-Commit-Position: refs/heads/master@{#577846}
[modify] https://crrev.com/b741423b44b8aa7ac5b1ab274ed8f77c3571a623/chrome/browser/consent_auditor/consent_auditor_factory.cc
[modify] https://crrev.com/b741423b44b8aa7ac5b1ab274ed8f77c3571a623/components/consent_auditor/consent_auditor_impl.cc
[modify] https://crrev.com/b741423b44b8aa7ac5b1ab274ed8f77c3571a623/components/consent_auditor/consent_auditor_impl.h
[modify] https://crrev.com/b741423b44b8aa7ac5b1ab274ed8f77c3571a623/components/consent_auditor/consent_auditor_impl_unittest.cc
[modify] https://crrev.com/b741423b44b8aa7ac5b1ab274ed8f77c3571a623/ios/chrome/browser/sync/consent_auditor_factory.cc

Stray copy/paste error, this bug is not related to b741423b44b8aa7ac5b1ab274ed8f77c3571a623.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e076f3a9ec5b30ce76b24479905758bdb8aa7645

commit e076f3a9ec5b30ce76b24479905758bdb8aa7645
Author: David Davidović <davidovic@google.com>
Date: Mon Aug 13 16:47:57 2018

[sync] Add CLI flag to capture specifics

When visiting chrome://sync-internals, a checkbox labeled "Capture
Specifics" is available. It controls whether the specifics of each sync
event are captured in the log displayed on the page.

Every time the page is refreshed or reopened, this checkbox is reset to
its initial, unchecked state. The flag is immensely useful for
debugging, but having to check the checkbox after each browser restart
or reopen of the page is cumbersome.

To that end, add a command-line switch "--sync-include-specifics" which
will set the initial value for the "Capture Specifics" flag on
chrome://sync-internals page load to true.

Bug:  859878 
Change-Id: I43b04e2d3aabdda2e8f3bc64cb80f906f56c78b2
Reviewed-on: https://chromium-review.googlesource.com/1147221
Commit-Queue: David Davidović <davidovic@google.com>
Reviewed-by: Marc Treib <treib@chromium.org>
Reviewed-by: vitaliii <vitaliii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582613}
[modify] https://crrev.com/e076f3a9ec5b30ce76b24479905758bdb8aa7645/chrome/browser/ui/webui/sync_internals_message_handler.cc
[modify] https://crrev.com/e076f3a9ec5b30ce76b24479905758bdb8aa7645/chrome/browser/ui/webui/sync_internals_message_handler.h
[modify] https://crrev.com/e076f3a9ec5b30ce76b24479905758bdb8aa7645/components/sync/driver/about_sync_util.cc
[modify] https://crrev.com/e076f3a9ec5b30ce76b24479905758bdb8aa7645/components/sync/driver/about_sync_util.h
[modify] https://crrev.com/e076f3a9ec5b30ce76b24479905758bdb8aa7645/components/sync/driver/resources/chrome_sync.js
[modify] https://crrev.com/e076f3a9ec5b30ce76b24479905758bdb8aa7645/components/sync/driver/resources/data.js
[modify] https://crrev.com/e076f3a9ec5b30ce76b24479905758bdb8aa7645/components/sync/driver/sync_driver_switches.cc
[modify] https://crrev.com/e076f3a9ec5b30ce76b24479905758bdb8aa7645/components/sync/driver/sync_driver_switches.h

To summarize: use the "--sync-include-specifics" command line switch and the "Capture Specifics" checkbox on chrome://sync-internals will default to checked (and will be capturing specifics from the moment it loads).