Update RRectBlur FP to use main(float2).
Update RRectBlur FP to use main(float2).

Change-Id: Iabf358a42e83b28d6e8480866be5aca9928550b2
Bug: skia:13737
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/580956
Auto-Submit: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Reviewed-by: Michael Ludwig <cb1f3dd24de0f0b611b26bc28bec758a551d9b7d@google.com>
Commit-Queue: Michael Ludwig <cb1f3dd24de0f0b611b26bc28bec758a551d9b7d@google.com>

google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia