Use GS wrapper to download from Google Storage.

This bug is blocking the Pre-CQ because we're seeing lots of failures
during remote trybot runs.

BUG=chromium:233226
TEST=Run it locally.
CQ-DEPEND=CL:48505
Change-Id: Iceb2bd970770735730254fe973cb914b5a1a9636
Reviewed-on: https://gerrit.chromium.org/gerrit/48533
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: David James <davidjames@chromium.org>
Tested-by: David James <davidjames@chromium.org>
2 files changed