Check in codegen test expectations.

test/codegen/expect/language/inference_mixin_field_test.js

+dart_library.library('language/inference_mixin_field_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__inference_mixin_field_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 inference_mixin_field_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  inference_mixin_field_test.Mixin = class Mixin extends core.Object {
+    new() {
+      this.field = null;
+    }
+    createIt() {
+      if (this.field == null) this.field = 42;
+    }
+  };
+  dart.setSignature(inference_mixin_field_test.Mixin, {
+    methods: () => ({createIt: dart.definiteFunctionType(dart.dynamic, [])})
+  });
+  inference_mixin_field_test.A = class A extends core.Object {
+    new(foo) {
+    }
+  };
+  dart.setSignature(inference_mixin_field_test.A, {
+    constructors: () => ({new: dart.definiteFunctionType(inference_mixin_field_test.A, [dart.dynamic])})
+  });
+  inference_mixin_field_test.B = class B extends dart.mixin(inference_mixin_field_test.A, inference_mixin_field_test.Mixin) {
+    new(foo) {
+      super.new(foo);
+    }
+  };
+  dart.setSignature(inference_mixin_field_test.B, {
+    constructors: () => ({new: dart.definiteFunctionType(inference_mixin_field_test.B, [dart.dynamic])})
+  });
+  inference_mixin_field_test.main = function() {
+    let a = new inference_mixin_field_test.B(42);
+    a.createIt();
+    expect$.Expect.equals(42, a.field);
+  };
+  dart.fn(inference_mixin_field_test.main, VoidTodynamic());
+  // Exports:
+  exports.inference_mixin_field_test = inference_mixin_field_test;
+});