packages.proto: Add HasChromePrebuilt method.

BUG=chromium:950006
TEST=./generate.sh

Change-Id: Ib40444afa1c9c90906664835bb81e1731d21f90c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/1807599
Tested-by: Alex Klein <saklein@chromium.org>
Auto-Submit: Alex Klein <saklein@chromium.org>
Reviewed-by: David Burger <dburger@chromium.org>
Commit-Queue: Alex Klein <saklein@chromium.org>
3 files changed