It will be easier to support centralized management of what footers exist if we
require all callers to specifically declare which footers they want to check.
This is a partial step towards allowing that without increasing the number of
queries required. It introduced cache staleness as a potential issue, but should
not matter in practice.

Bug: chromium:1079219
Change-Id: I678fd366202bac5a4efa4258ffe02e70c64589bb
Recipe-Nontrivial-Roll: infra
Recipe-Nontrivial-Roll: chromiumos
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2664790
Commit-Queue: Jacob Kopczynski <jkop@chromium.org>
Auto-Submit: Jacob Kopczynski <jkop@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>