Also add a presubmit so they don't get added to source code.
Change-Id: I6a85c6a934b1068a63646a0dcc0d3a08baa96ced
Reviewed-on: https://skia-review.googlesource.com/57110
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>