[FedCM] Share more code between OnResolve and CompleteTokenRequest
In particular, this makes us call SetRequiresUserMediation also for
OnResolve.
Bug: 349994201
Change-Id: I0d0f4d374e9ab601eb603d714930074923789218
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5673234
Commit-Queue: Christian Biesinger cbiesinger@chromium.org
Reviewed-by: Yi Gu yigu@chromium.org
Cr-Commit-Position: refs/heads/main@{#1322994}