"API replacement summary:
- AccountTrackerService::Observer::OnAccountUpdated => IdentityManager::Observer::OnAccountUpdated
- AccountTrackerService::Observer::OnAccountRemoved => IdentityManager::Observer::OnAccountRemovedWithInfo
- AccountTrackerService::GetAccountInfo => IdentityManager::FindAccountInfoForAccountWithRefreshTokenByAccountId
- AccountTrackerService::GetAccountImage => IdentityManager::FindAccountInfoForAccountWithRefreshTokenByAccountId
- AccountTrackerService::FindAccountInfoByEmail => IdentityManager::FindAccountInfoForAccountWithRefreshTokenByEmailAddress
"

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8b171daf36371e7270b7a8fa44d90b00015381d5

commit 8b171daf36371e7270b7a8fa44d90b00015381d5
Author: Julie Jeongeun Kim <jkim@igalia.com>
Date: Tue Jan 22 23:02:14 2019

[s13n] Move PeopleHandler away from AccountTrackerService

This CL removes AccountTrackerService::Observer from PeopleHandler
as it can get OnAccountUpdated/OnAccountRemovedWithInfo through
IdentityManager::Observer.

Bug:  922787 
Change-Id: Ifb9a605f27bcadf991858836a813c5e80bbff556
Reviewed-on: https://chromium-review.googlesource.com/c/1426204
Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Commit-Queue: Julie Jeongeun Kim <jkim@igalia.com>
Cr-Commit-Position: refs/heads/master@{#624978}
[modify] https://crrev.com/8b171daf36371e7270b7a8fa44d90b00015381d5/chrome/browser/ui/webui/settings/people_handler.cc
[modify] https://crrev.com/8b171daf36371e7270b7a8fa44d90b00015381d5/chrome/browser/ui/webui/settings/people_handler.h