Check in codegen test expectations.

test/codegen/expect/language/issue9602_test.js

Index: test/codegen/expect/language/issue9602_test.js
diff --git a/test/codegen/expect/language/issue9602_test.js b/test/codegen/expect/language/issue9602_test.js
new file mode 100644
index 0000000000000000000000000000000000000000..54a5e94639328938065f7c4d1c627f58162fe56e
--- /dev/null
+++ b/test/codegen/expect/language/issue9602_test.js
@@ -0,0 +1,29 @@
+dart_library.library('language/issue9602_test', null, /* Imports */[
+  'dart_sdk'
+], function load__issue9602_test(exports, dart_sdk) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const issue9602_test = Object.create(null);
+  const issue9602_other = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  const _field = Symbol('_field');
+  issue9602_other.M = class M extends core.Object {
+    new() {
+      this[_field] = null;
+    }
+  };
+  issue9602_test.C = class C extends dart.mixin(core.Object, issue9602_other.M) {
+    new() {
+      super.new();
+    }
+  };
+  issue9602_test.main = function() {
+    new issue9602_test.C();
+  };
+  dart.fn(issue9602_test.main, VoidTodynamic());
+  // Exports:
+  exports.issue9602_test = issue9602_test;
+  exports.issue9602_other = issue9602_other;
+});