Sets UIPinchGestureRecognizer and UISwipeGestureRecognizers and
passes the result down to the sk_app::Window. To simplify detection,
swipes take precedence over pans, and pans require a single touch.
This is less flexible for the app, but in most cases I think is
what we want.
Bug: skia:8737
Change-Id: Ib031b6ad465d3a353da29d7e0b48a666d4ff8b9a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/239776
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
d0cf5da20d