Check in codegen test expectations.

test/codegen/expect/language/return_this_type_test.js

Index: test/codegen/expect/language/return_this_type_test.js
diff --git a/test/codegen/expect/language/return_this_type_test.js b/test/codegen/expect/language/return_this_type_test.js
new file mode 100644
index 0000000000000000000000000000000000000000..a1288e84363d44ad4045fb60858bb5034a2ddf78
--- /dev/null
+++ b/test/codegen/expect/language/return_this_type_test.js
@@ -0,0 +1,27 @@
+dart_library.library('language/return_this_type_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__return_this_type_test(exports, dart_sdk, expect) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const expect$ = expect.expect;
+  const return_this_type_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  return_this_type_test.A = class A extends core.Object {
+    foo() {
+      return this;
+    }
+  };
+  dart.setSignature(return_this_type_test.A, {
+    methods: () => ({foo: dart.definiteFunctionType(dart.dynamic, [])})
+  });
+  return_this_type_test.B = class B extends return_this_type_test.A {};
+  return_this_type_test.main = function() {
+    expect$.Expect.isTrue(return_this_type_test.B.is(new return_this_type_test.B().foo()));
+  };
+  dart.fn(return_this_type_test.main, VoidTodynamic());
+  // Exports:
+  exports.return_this_type_test = return_this_type_test;
+});