Name common cubic resamplers

Useful in client code to document what we're doing as we switch away
from SkFilterQuality.

Change-Id: I05737beb99a567a46a3c3ec418b7f7da71b1ff62
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/366723
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/gm/perspshaders.cpp b/gm/perspshaders.cpp
index 96d2433..24073d0 100644
--- a/gm/perspshaders.cpp
+++ b/gm/perspshaders.cpp
@@ -157,7 +157,7 @@
         this->drawRow(canvas, SkSamplingOptions(SkFilterMode::kLinear,
                                                 SkMipmapMode::kNearest));
         canvas->translate(0, SkIntToScalar(kCellSize));
-        this->drawRow(canvas, SkSamplingOptions({1.0f/3, 1.0f/3}));
+        this->drawRow(canvas, SkSamplingOptions(SkCubicResampler::Mitchell()));
         canvas->translate(0, SkIntToScalar(kCellSize));
     }
 private: