Check in codegen test expectations.

test/codegen/expect/language/mixin_forwarding_constructor1_test.js

+dart_library.library('language/mixin_forwarding_constructor1_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__mixin_forwarding_constructor1_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_forwarding_constructor1_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  mixin_forwarding_constructor1_test.Mixin1 = class Mixin1 extends core.Object {
+    new() {
+      this.mixin1Field = 1;
+    }
+  };
+  mixin_forwarding_constructor1_test.Mixin2 = class Mixin2 extends core.Object {
+    new() {
+      this.mixin2Field = 2;
+    }
+  };
+  mixin_forwarding_constructor1_test.A = class A extends core.Object {
+    new(foo) {
+      this.superField = foo;
+    }
+  };
+  dart.setSignature(mixin_forwarding_constructor1_test.A, {
+    constructors: () => ({new: dart.definiteFunctionType(mixin_forwarding_constructor1_test.A, [dart.dynamic])})
+  });
+  mixin_forwarding_constructor1_test.B = class B extends dart.mixin(mixin_forwarding_constructor1_test.A, mixin_forwarding_constructor1_test.Mixin1, mixin_forwarding_constructor1_test.Mixin2) {
+    new(unused) {
+      this.field = 4;
+      super.new(3);
+    }
+  };
+  dart.setSignature(mixin_forwarding_constructor1_test.B, {
+    constructors: () => ({new: dart.definiteFunctionType(mixin_forwarding_constructor1_test.B, [dart.dynamic])})
+  });
+  mixin_forwarding_constructor1_test.main = function() {
+    let b = new mixin_forwarding_constructor1_test.B(null);
+    expect$.Expect.equals(1, b.mixin1Field);
+    expect$.Expect.equals(2, b.mixin2Field);
+    expect$.Expect.equals(3, b.superField);
+    expect$.Expect.equals(4, b.field);
+  };
+  dart.fn(mixin_forwarding_constructor1_test.main, VoidTodynamic());
+  // Exports:
+  exports.mixin_forwarding_constructor1_test = mixin_forwarding_constructor1_test;
+});