converted EllipseEffect to sksl

Bug: skia:
Change-Id: Id089b9ead7a21e903b001006dffff2381efd4ba3
Reviewed-on: https://skia-review.googlesource.com/23582
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
6 files changed