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/clippedbitmapshaders.cpp b/gm/clippedbitmapshaders.cpp
index 8680865..095921c 100644
--- a/gm/clippedbitmapshaders.cpp
+++ b/gm/clippedbitmapshaders.cpp
@@ -92,7 +92,7 @@
         s.postTranslate(SLIDE_SIZE / 2, SLIDE_SIZE / 2);
         SkPaint paint;
         paint.setShader(bmp.makeShader(fMode, fMode,
-                                       fHQ ? SkSamplingOptions({1.0f/3, 1.0f/3})
+                                       fHQ ? SkSamplingOptions(SkCubicResampler::Mitchell())
                                            : SkSamplingOptions(),
                                        s));