fix variable sample matrices in FP files

Change-Id: I7bcfdd821d004529231a6d082528538c796858d0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/291956
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/src/sksl/SkSLHCodeGenerator.cpp b/src/sksl/SkSLHCodeGenerator.cpp
index 8a6f350..ebe05e8 100644
--- a/src/sksl/SkSLHCodeGenerator.cpp
+++ b/src/sksl/SkSLHCodeGenerator.cpp
@@ -290,8 +290,8 @@
             SampleMatrix matrix = fSectionAndParameterHelper.getMatrix(*param);
             switch (matrix.fKind) {
                 case SampleMatrix::Kind::kVariable:
-                    this->writef("            %s->setSampleMatrix(this, "
-                                                            "SkSL::SampleMatrix::Kind::kVariable);",
+                    this->writef("            %s->setSampleMatrix(SkSL::SampleMatrix("
+                                                     "SkSL::SampleMatrix::Kind::kVariable));",
                                  String(param->fName).c_str());
                     break;
                 case SampleMatrix::Kind::kConstantOrUniform: