The verifier will work with both crx2 and crx3 (at least, until crx2 is
gone forever...)

Bug: 970891
Change-Id: I85665748a816e952f80df6e5509fb71fc0743d77
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1643353Reviewed-by: John Chen <johnchen@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Joshua Pawlicki <waffles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666330}