These are free functions which get the SigninManager as a parameter. We need to provide new function that take an IdentityManager instead. So here is the plan:

1 (done)- Add dual functions taking IdentityManager as a parameter in the .h file.
2 (done)- Implement those function in the .cpp file
3 (done)- Find all the includes of the .h file. There are 4 of them
4 (tbd) - convert those 4 files to use the new dual functions
5 (tbd) - test. I need to find out how.
6 (tbd) - remove the old functions

the 4 client files:
components/password_manager/sync/browser/sync_credentials_filter.cc
components/password_manager/sync/browser/password_sync_util_unittest.cc
chrome/browser/ui/passwords/password_manager_presenter.cc
chrome/browser/password_manager/chrome_password_manager_client.cc

the sync code containing these source files has been removed, and thus these files do not exist any more.

see https://chromium-review.googlesource.com/c/chromium/src/+/1252583