Move setSampleMatrix and setSampledWithExplicitCoords into child registration

Bug: skia:10396
Change-Id: I0c117ab4d95737b76dec5bce16103b9058218fb8
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/297065
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/src/gpu/SkGr.cpp b/src/gpu/SkGr.cpp
index 2e0cb32..94abf6b 100644
--- a/src/gpu/SkGr.cpp
+++ b/src/gpu/SkGr.cpp
@@ -387,7 +387,7 @@
             if (ditherFP) {
                 // The dither shader doesn't actually use input coordinates, but if we don't set
                 // this flag, the generated shader includes an extra local coord varying.
-                ditherFP->setSampledWithExplicitCoords();
+                ditherFP->temporary_SetExplicitlySampled();
                 grPaint->addColorFragmentProcessor(std::move(ditherFP));
             }
         }