Log referrer chain length by verdict type

When Chrome gets password protection verdicts from Safe Browsing, we'd
like to log the referrer chain size by verdict type.

Bug: 864608
Change-Id: If11cd732c6c45865a64bfbbccf71af4615b148f9
Reviewed-on: https://chromium-review.googlesource.com/1141179
Commit-Queue: Jialiu Lin <jialiul@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576367}
4 files changed