clone saturating cast code for doubles

Bug: skia:
Change-Id: I4f35413995cf73c6f130476d6b36e530120aa7ed
Reviewed-on: https://skia-review.googlesource.com/57901
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Reed <reed@google.com>
3 files changed