The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2eef915019e671ac95d7b6f47bde8601d25e8477

commit 2eef915019e671ac95d7b6f47bde8601d25e8477
Author: Tanja Gornak <melandory@chromium.org>
Date: Wed Dec 12 11:14:52 2018

[Tango->FCM] Remove topic from saved prefs  before the request has finished.


* As of today, when subscription to the topic gets deleted,
the value in prefs is cleaned up only after the response for HTTP
unsubscription request arrives.
* It can happen, e.g. on the browser shutdown that the clean-up
code is never executed, hence prefs won't be cleaned up.
* This CL makes the prefs cleanup happen when the decision to unsubscribe
from the topic notifications is made.

BUG= 913486 

Change-Id: I3d58df8896ef87ecef4535fb588d9a73494c2de1
Reviewed-on: https://chromium-review.googlesource.com/c/1370164
Commit-Queue: Tatiana Gornak <melandory@chromium.org>
Reviewed-by: Jan Krcal <jkrcal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615852}
[modify] https://crrev.com/2eef915019e671ac95d7b6f47bde8601d25e8477/components/invalidation/impl/per_user_topic_registration_manager.cc
[modify] https://crrev.com/2eef915019e671ac95d7b6f47bde8601d25e8477/components/invalidation/impl/per_user_topic_registration_manager_unittest.cc

This bug requires manual review: M72 has already been promoted to the beta branch, so this requires manual review
Please contact the milestone owner if you have questions.
Owners: govind@(Android), kariahda@(iOS), djmm@(ChromeOS), abdulsyed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Why is this critical for M72 vs waiting til 73? How safe is this merge?

The merge is safe. For privacy reasons, I'd prefer to have it in M72

This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

If all merges have been completed, please remove any remaining Merge-Approved labels from this issue.

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For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

If all merges have been completed, please remove any remaining Merge-Approved labels from this issue.

Thanks for your time! To disable nags, add the Disable-Nags label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot