writer/wgsl: Remove builtin unit test

This test is invalid for multiple reasons (wrong types, wrong stages,
global variable instead of a parameter). The shader IO E2E tests give
better coverage for this anyway, so just delete the unit test.

Change-Id: I1627addf1e407e473e33043341d742958ceebca5
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/55861
Auto-Submit: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/writer/wgsl/generator_impl_test.cc

@@ -34,48 +34,6 @@ TEST_F(WgslGeneratorImplTest, Generate) {
 )");
 }
 
-struct WgslBuiltinData {
-  ast::Builtin builtin;
-  const char* attribute_name;
-};
-inline std::ostream& operator<<(std::ostream& out, WgslBuiltinData data) {
-  out << data.builtin;
-  return out;
-}
-using WgslBuiltinConversionTest = TestParamHelper<WgslBuiltinData>;
-TEST_P(WgslBuiltinConversionTest, Emit) {
-  auto params = GetParam();
-
-  auto* var = Global("a", ty.f32(), ast::StorageClass::kPrivate, nullptr,
-                     ast::DecorationList{
-                         Builtin(params.builtin),
-                     });
-
-  GeneratorImpl& gen = Build();
-
-  gen.EmitDecorations(var->decorations());
-
-  EXPECT_EQ(gen.result(),
-            "[[builtin(" + std::string(params.attribute_name) + ")]]");
-}
-INSTANTIATE_TEST_SUITE_P(
-    WgslGeneratorImplTest,
-    WgslBuiltinConversionTest,
-    testing::Values(
-        WgslBuiltinData{ast::Builtin::kPosition, "position"},
-        WgslBuiltinData{ast::Builtin::kVertexIndex, "vertex_index"},
-        WgslBuiltinData{ast::Builtin::kInstanceIndex, "instance_index"},
-        WgslBuiltinData{ast::Builtin::kFrontFacing, "front_facing"},
-        WgslBuiltinData{ast::Builtin::kFragDepth, "frag_depth"},
-        WgslBuiltinData{ast::Builtin::kLocalInvocationId,
-                        "local_invocation_id"},
-        WgslBuiltinData{ast::Builtin::kLocalInvocationIndex,
-                        "local_invocation_index"},
-        WgslBuiltinData{ast::Builtin::kGlobalInvocationId,
-                        "global_invocation_id"},
-        WgslBuiltinData{ast::Builtin::kWorkgroupId, "workgroup_id"},
-        WgslBuiltinData{ast::Builtin::kSampleIndex, "sample_index"}));
-
 }  // namespace
 }  // namespace wgsl
 }  // namespace writer