Sync: failed DCHECK when delete device record arrives twice

[AlexeyBarabash]

Description

If two delete device records arrives to sync service, there is a failed DCHECK

[83053:775:0103/160933.609992:FATAL:sync_devices.cc(175)] Check failed: existing_it != std::end(devices_).

brave/brave-core#1193 (comment)

Steps to Reproduce

No steps to reproduce for QA, because this appears on debug builds only.
Could be reproduced with a related PR unit-test.

Brave version (brave://version info)

Version 0.61.0 Chromium: 72.0.3626.28 (Developer Build) (64-bit)

Reproducible on current release:

• Does it reproduce on brave-browser dev/beta builds?
  no

[kjozwiak]

@AlexeyBarabash can this issue negatively affect users on production? It's labelled as P3 but the issue mentions that it only happens in debug mode. If this is going to cause issues when users are removing devices, we should fix this before releasing sync in 0.59.x.

[AlexeyBarabash]

@kjozwiak correct, this issue cannot negatively affect users on production, this appears only in debug builds.
This is not going to cause issues when users are removing devices.

[AlexeyBarabash]

Closed with brave/brave-core#1125 .

[rebron]

@AlexeyBarabash can you set the right milestone for this?

[kjozwiak]

brave/brave-core#1125 should also have a milestone 👍

[AlexeyBarabash]

Thanks @rebron @kjozwiak , just had set the correct milestones.