Check in codegen test expectations.

test/codegen/expect/language/mixin_mixin_test.js

Index: test/codegen/expect/language/mixin_mixin_test.js
diff --git a/test/codegen/expect/language/mixin_mixin_test.js b/test/codegen/expect/language/mixin_mixin_test.js
new file mode 100644
index 0000000000000000000000000000000000000000..ebc60c5274c360cc9dcbe853a8ac221bf93d31ad
--- /dev/null
+++ b/test/codegen/expect/language/mixin_mixin_test.js
@@ -0,0 +1,38 @@
+dart_library.library('language/mixin_mixin_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__mixin_mixin_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 mixin_mixin_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  mixin_mixin_test.M1 = class M1 extends core.Object {
+    foo() {
+      return 42;
+    }
+  };
+  dart.setSignature(mixin_mixin_test.M1, {
+    methods: () => ({foo: dart.definiteFunctionType(dart.dynamic, [])})
+  });
+  mixin_mixin_test.M2 = class M2 extends dart.mixin(core.Object, mixin_mixin_test.M1) {};
+  mixin_mixin_test.S = class S extends core.Object {};
+  mixin_mixin_test.C = class C extends dart.mixin(mixin_mixin_test.S, mixin_mixin_test.M2) {
+    new() {
+      super.new();
+    }
+  };
+  mixin_mixin_test.main = function() {
+    let c = new mixin_mixin_test.C();
+    expect$.Expect.isTrue(mixin_mixin_test.S.is(c));
+    expect$.Expect.isTrue(mixin_mixin_test.M1.is(c));
+    expect$.Expect.isTrue(mixin_mixin_test.M2.is(c));
+    expect$.Expect.isTrue(mixin_mixin_test.C.is(c));
+    expect$.Expect.equals(42, c.foo());
+  };
+  dart.fn(mixin_mixin_test.main, VoidTodynamic());
+  // Exports:
+  exports.mixin_mixin_test = mixin_mixin_test;
+});