The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4aff22082191c4789c7102ab7b957a04898e2806

commit 4aff22082191c4789c7102ab7b957a04898e2806
Author: Varun Khaneja <vakh@chromium.org>
Date: Fri Sep 22 14:50:45 2017

Delete PVer3 store files with UMA logging.

As noted in the comment, once the UMA metric for prefix
"SafeBrowsing.V4UnusedStoreFileExists.V3." goes down to 0, it is safe to
remove this code.

Bug:  754543 
Change-Id: I01c40b6b339418a163ec4da0b6c511e995da75b9
Reviewed-on: https://chromium-review.googlesource.com/677479
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Jialiu Lin <jialiul@chromium.org>
Reviewed-by: Luke Z <lpz@chromium.org>
Commit-Queue: Varun Khaneja <vakh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503736}
[modify] https://crrev.com/4aff22082191c4789c7102ab7b957a04898e2806/components/safe_browsing/db/v4_local_database_manager.cc
[modify] https://crrev.com/4aff22082191c4789c7102ab7b957a04898e2806/components/safe_browsing/db/v4_local_database_manager.h
[modify] https://crrev.com/4aff22082191c4789c7102ab7b957a04898e2806/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8418d476fc80b7f82e282d159616935dd24652bf

commit 8418d476fc80b7f82e282d159616935dd24652bf
Author: Varun Khaneja <vakh@chromium.org>
Date: Fri Sep 22 21:12:26 2017

Delete two more PVer3 lists that I missed earlier

I missed them because I did not have them in my local Safe Browsing
directory. The "Side-Effect Free Whitelist" seems to have been
deprecated 2 years ago.

Follow-up from https://crrev.com/c/677479

Bug:  754543 
Change-Id: I2359fb0de6b622ad8f3ee9f04cd6a9a05333b51c
Reviewed-on: https://chromium-review.googlesource.com/679259
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Jialiu Lin <jialiul@chromium.org>
Commit-Queue: Varun Khaneja <vakh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503852}
[modify] https://crrev.com/8418d476fc80b7f82e282d159616935dd24652bf/components/safe_browsing/db/v4_local_database_manager.cc
[modify] https://crrev.com/8418d476fc80b7f82e282d159616935dd24652bf/tools/metrics/histograms/histograms.xml

Tracked here: http://shortn/_gEPdgOfzdO

Actually, here: http://shortn/_4C0WYjJKDW

The changes landed in "63.0.3223.0"

http://shortn/_c4Z7pySTHJ shows that all PVer3 files are now showing as deleted for >99% users on C/D/B channels.