Optimize GrRRectBlurEffect by computing frag pos branchlessly.

This version computes X and Y in parallel and without branching.

Change-Id: I08dd7339f75c6cdd5b4130bf363cac1f527bf6ed
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/295572
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
3 files changed