Fixed function analysis line numbers with DSLParser

Bug: skia:12412
Change-Id: I0f64e2941a2a87fa49b171a2a3d34517f20b58ca
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/449100
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/src/sksl/dsl/DSLFunction.cpp b/src/sksl/dsl/DSLFunction.cpp
index 946798c..f743ed7 100644
--- a/src/sksl/dsl/DSLFunction.cpp
+++ b/src/sksl/dsl/DSLFunction.cpp
@@ -98,7 +98,7 @@
     // Append sk_Position fixup to the bottom of main() if this is a vertex program.
     DSLWriter::IRGenerator().appendRTAdjustFixupToVertexMain(*fDecl, body.get());
     std::unique_ptr<FunctionDefinition> function = FunctionDefinition::Convert(DSLWriter::Context(),
-                                                                               /*offset=*/-1,
+                                                                               pos.offset(),
                                                                                *fDecl,
                                                                                std::move(body),
                                                                                /*builtin=*/false);