GitLab

The logic here is easier if the unsupported cases are rejected first.

Change-Id: I231935618dea789972934e7cd09ec3616744b9e7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1725209Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Adam Langley <agl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682392}