add -Tidy bot

Change-Id: Ia8d942735cdd1c52a78be02b53f532433abacbc4
Reviewed-on: https://skia-review.googlesource.com/c/176977
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
5 files changed