The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8c2893ee9102687d16f2f65fa96651d8bd1fdab7

commit 8c2893ee9102687d16f2f65fa96651d8bd1fdab7
Author: Patti <patricialor@chromium.org>
Date: Fri Oct 12 06:10:28 2018

Revert "[Tango->FCM] Do not perform bulk unregistering on shutdown and on handler unregistering."

This reverts commit 86da6573944f302cf9df04d59a7e35bba895d059.

Reason for revert: This patch may be causing failures in browser_tests, on chromium.win/Win7 Tests (dbg)(1)
  https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win7%20Tests%20%28dbg%29%281%29

Findit found culprit 598844 with 75% confidence, so reverting this to try and fix.

Original change's description:
> [Tango->FCM] Do not perform bulk unregistering on shutdown and on handler unregistering.
> 
> * The service shouldn't unregister from the topics, when handler
> the Handler is unregistering from topic (as stated in the documentation
> for for UnregisterHandler).
> * Sync shouldn't unregister on browser shutdown
> 
> Bug: 801985,  876274 
> Change-Id: I857da7b0fbfa0a0f2e1ad05708cc24cdc9386a76
> Reviewed-on: https://chromium-review.googlesource.com/c/1196522
> Commit-Queue: Tatiana Gornak <melandory@chromium.org>
> Reviewed-by: Gabriel Charette <gab@chromium.org>
> Reviewed-by: Pavel Yatsuk <pavely@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#598844}

TBR=gab@chromium.org,pavely@chromium.org,melandory@chromium.org

Change-Id: I70fa87c3476925814408665644acb23c3c1f1614
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 801985,  876274 ,  894715 
Reviewed-on: https://chromium-review.googlesource.com/c/1278273
Reviewed-by: Patti <patricialor@chromium.org>
Commit-Queue: Patti <patricialor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599111}
[modify] https://crrev.com/8c2893ee9102687d16f2f65fa96651d8bd1fdab7/chrome/browser/prefs/browser_prefs.cc
[modify] https://crrev.com/8c2893ee9102687d16f2f65fa96651d8bd1fdab7/components/invalidation/impl/BUILD.gn
[modify] https://crrev.com/8c2893ee9102687d16f2f65fa96651d8bd1fdab7/components/invalidation/impl/fcm_fake_invalidator.cc
[modify] https://crrev.com/8c2893ee9102687d16f2f65fa96651d8bd1fdab7/components/invalidation/impl/fcm_invalidation_listener.cc
[modify] https://crrev.com/8c2893ee9102687d16f2f65fa96651d8bd1fdab7/components/invalidation/impl/fcm_invalidation_listener.h
[modify] https://crrev.com/8c2893ee9102687d16f2f65fa96651d8bd1fdab7/components/invalidation/impl/fcm_invalidation_service.cc
[modify] https://crrev.com/8c2893ee9102687d16f2f65fa96651d8bd1fdab7/components/invalidation/impl/fcm_invalidation_service.h
[modify] https://crrev.com/8c2893ee9102687d16f2f65fa96651d8bd1fdab7/components/invalidation/impl/fcm_invalidation_service_unittest.cc
[modify] https://crrev.com/8c2893ee9102687d16f2f65fa96651d8bd1fdab7/components/invalidation/impl/invalidator_registrar.cc
[modify] https://crrev.com/8c2893ee9102687d16f2f65fa96651d8bd1fdab7/components/invalidation/impl/invalidator_registrar.h
[delete] https://crrev.com/f93617e5eb9f06935b07002223f33d164f517909/components/invalidation/impl/invalidator_registrar_with_memory.cc
[delete] https://crrev.com/f93617e5eb9f06935b07002223f33d164f517909/components/invalidation/impl/invalidator_registrar_with_memory.h
[modify] https://crrev.com/8c2893ee9102687d16f2f65fa96651d8bd1fdab7/components/sync/driver/glue/sync_backend_host_impl.cc