As mentioned by @msarda in [1], it would be nice to convert this method into one that takes a OnceCallback instead of a base::Closure, to make it explicit that such callback is only meant to be run once.

This ticket tracks that effort.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/1425500/4/components/signin/core/browser/mutable_profile_oauth2_token_service_delegate.cc#264