Reland "Convert GrDitherEffect to a runtime FP"

This reverts commit 3dd52c758b6cbcf1bf6eca1d0a594195e770d2ef.

Change-Id: Ie873ad570ffc57b3edd6ffe8612cbc2c73d40450
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/424259
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/src/gpu/GrProcessorUnitTest.cpp b/src/gpu/GrProcessorUnitTest.cpp
index 3a6f0d1..b4c673f 100644
--- a/src/gpu/GrProcessorUnitTest.cpp
+++ b/src/gpu/GrProcessorUnitTest.cpp
@@ -146,7 +146,7 @@
  * we verify the count is as expected.  If a new factory is added, then these numbers must be
  * manually adjusted.
  */
-static constexpr int kFPFactoryCount = 18;
+static constexpr int kFPFactoryCount = 17;
 static constexpr int kGPFactoryCount = 14;
 static constexpr int kXPFactoryCount = 4;