Swarming protos

Source:

• Repo: https://chromium.googlesource.com/infra/luci/luci-py
• Path: appengine/swarming/proto
• Revision: d9447bf7fe1c3663526b78f4c87ef5a6473a7c0f

Updating

Run ./update.sh. It will pull in protos, regenerate go code and update the revision in this file.