Fix explanation for edge case in FederatedAuthRequestImpl
This CL updates the explanation for the edge case in
FederatedAuthRequestImpl::CancelTokenRequest() and adds test which
executes the edge case.
BUG=40940748
Change-Id: I800959c721f13364801110eb20b1e1dff0b45059
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5871992
Commit-Queue: Peter Kotwicz pkotwicz@chromium.org
Reviewed-by: Christian Biesinger cbiesinger@chromium.org
Cr-Commit-Position: refs/heads/main@{#1357306}