Convert AccountTrackerService api to use CoreAccountId instead of std::string

This cl is part of the effort to replace use of std::string as account_id
and instead use strongly typed CoreAccountId to clear ambiguity.

Bug: 959157
Change-Id: I84b449d6bbbf6cfd1081440c9f3a8441e8998f36
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1605903
Commit-Queue: Tanmoy Mollik <triploblastic@google.com>
Reviewed-by: David Roger <droger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660415}
2 files changed