Use raster pipeline for repeat/mirror radial gradients

The legacy clamp specialization is still faster, but for repeat and
mirror RP wins (at low color stop counts).

Change-Id: Ifef3eb5b3111b3741d3a033310a4cdb58e592247
Reviewed-on: https://skia-review.googlesource.com/24283
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
2 files changed