saturate IPoint math, handle NaN in isEmpty

Bug: skia:7507
Change-Id: Ibdb40584effdea70e6499eab1bb64bb4b2260d06
Reviewed-on: https://skia-review.googlesource.com/106972
Commit-Queue: Mike Reed <reed@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
4 files changed