Add nanobench entries for Graphite Metal/WGSL large shaders.

This effect matches the equivalent Ganesh draw, which is a
fragment shader from a conical gradient.

I don't have a nanobench for medium or small yet. The current
nanobench effect for medium in Ganesh comes from
GM_BlurDrawImage, and we don't have blurs in Graphite yet. The
current small effect comes from GM_lcdtext, which does work in
Graphite, but its shader has not yet been migrated into the
Graphite module, so it's not representative of the finished
product.

Change-Id: I26d22504a0fed5ff6adb61ab3da9a134d6e850d3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/741440
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
1 file changed