Add sample(child, matrix) to SkSL.

This allows fragment processors to sample their children with their
local coordinate system transformed by a matrix.

Change-Id: Ifa848bbd85b939bbc5751fec5cf8f89ee904bf39
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/282590
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/src/gpu/gradients/generated/GrSweepGradientLayout.cpp b/src/gpu/gradients/generated/GrSweepGradientLayout.cpp
index d9d354f..cd4653a 100644
--- a/src/gpu/gradients/generated/GrSweepGradientLayout.cpp
+++ b/src/gpu/gradients/generated/GrSweepGradientLayout.cpp
@@ -33,8 +33,8 @@
                                                    "bias");
         scaleVar = args.fUniformHandler->addUniform(&_outer, kFragment_GrShaderFlag, kHalf_GrSLType,
                                                     "scale");
-        SkString sk_TransformedCoords2D_0 =
-                fragBuilder->ensureCoords2D(args.fTransformedCoords[0].fVaryingPoint);
+        SkString sk_TransformedCoords2D_0 = fragBuilder->ensureCoords2D(
+                args.fTransformedCoords[0].fVaryingPoint, _outer.sampleMatrix());
         fragBuilder->codeAppendf(
                 "half angle;\nif (sk_Caps.atan2ImplementedAsAtanYOverX) {\n    angle = half(2.0 * "
                 "atan(-%s.y, length(%s) - %s.x));\n} else {\n    angle = half(atan(-%s.y, "