[Passwords] Add Time Metrics for Leak Detection

This change adds time metrics for the leak detection feature.

Bug: 986298
Change-Id: Ida4bdd50adfa5d9b3fda910f70a26375b5031525
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1760921
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Auto-Submit: Jan Wilken Dörrie <jdoerrie@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#688933}