findmissing: Add chromeos-5.15 and v5.15.y

Add support for the latest ChromeOS branch and the latest longterm
stable release.

BUG=None
TEST=Run robot

Change-Id: I96de93cda7535530efdafecef5c61c998c83caeb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/3400355
Tested-by: Guenter Roeck <groeck@chromium.org>
Auto-Submit: Guenter Roeck <groeck@chromium.org>
Reviewed-by: Curtis Malainey <cujomalainey@chromium.org>
Commit-Queue: Curtis Malainey <cujomalainey@chromium.org>
1 file changed