Add bb to depot_tools

Bug: 946422
Change-Id: I7f1e5463b7bb1170124c94066b660a1b972884bf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1550200
Commit-Queue: Nodir Turakulov <nodir@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>