allow path.add(path) safely

Bug: 882423
Change-Id: Ied2ad2d5dfdf00af8f3ba722b522e9602fea5557
Reviewed-on: https://skia-review.googlesource.com/153260
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed