Show Download Protection referrer chain on chrome://safe-browsing

When we send a download ping, show the referrer chain so that problems
with the referrer chain logic can be debugged.

Bug: 865761
Change-Id: Id3f5dac4345b9cf179dee80417f99d94f3c3d7b0
Reviewed-on: https://chromium-review.googlesource.com/1150573
Reviewed-by: Varun Khaneja <vakh@chromium.org>
Commit-Queue: Daniel Rubery <drubery@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578379}
1 file changed