Add a test to ensure []byte => BlobKey PLS works.
Add a test to ensure []byte => BlobKey PLS works.

R=iannucci@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1616033004

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go