Migrate swizzle tests to golden SkSL files.

This simplifies life when revising the swizzle logic.

Change-Id: I7fc63c0cc845c4741c17c82b3078040264b61ba0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/317379
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/gn/sksl_tests.gni b/gn/sksl_tests.gni
index 8a21c28..c42e86c 100644
--- a/gn/sksl_tests.gni
+++ b/gn/sksl_tests.gni
@@ -55,6 +55,9 @@
   "$_tests/sksl/glsl/Switch.sksl",
   "$_tests/sksl/glsl/SwitchContainingDeadCode.sksl",
   "$_tests/sksl/glsl/SwitchWithFallthrough.sksl",
+  "$_tests/sksl/glsl/SwizzleConstants.sksl",
+  "$_tests/sksl/glsl/SwizzleOpt.sksl",
+  "$_tests/sksl/glsl/SwizzleScalar.sksl",
   "$_tests/sksl/glsl/UnusedVariables.sksl",
   "$_tests/sksl/glsl/VectorConstructors.sksl",
   "$_tests/sksl/glsl/VectorFolding.sksl",