Add cert dimension for Mac Builders.

This will make it easier to transition to new cert.

Bug: skia:7408
Change-Id: I9263851233f492c5e62155b61541783aa86ba634
Reviewed-on: https://skia-review.googlesource.com/85006
Reviewed-by: Stephan Altmueller <stephana@google.com>
Commit-Queue: Ben Wagner <benjaminwagner@google.com>
2 files changed