Update GrBlurredEdgeFragmentProcessor to use a child FP.

We are updating FPs to receive their input via a child FP where
possible, instead of relying on the input color.

Change-Id: Ib2bac2c7865d4285fbbf45c9de29bbd4d139d04b
Bug: skia:10217
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/294396
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
4 files changed