Check in codegen test expectations.

test/codegen/expect/language/regress_20394_test_none_multi.js

+dart_library.library('language/regress_20394_test_none_multi', null, /* Imports */[
+  'dart_sdk'
+], function load__regress_20394_test_none_multi(exports, dart_sdk) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const regress_20394_test_none_multi = Object.create(null);
+  const regress_20394_lib = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  regress_20394_test_none_multi.M = class M extends core.Object {};
+  regress_20394_lib.Super = class Super extends core.Object {
+    new() {
+    }
+    _private(arg) {
+    }
+  };
+  dart.defineNamedConstructor(regress_20394_lib.Super, '_private');
+  dart.setSignature(regress_20394_lib.Super, {
+    constructors: () => ({
+      new: dart.definiteFunctionType(regress_20394_lib.Super, []),
+      _private: dart.definiteFunctionType(regress_20394_lib.Super, [dart.dynamic])
+    })
+  });
+  regress_20394_test_none_multi.C = class C extends dart.mixin(regress_20394_lib.Super, regress_20394_test_none_multi.M) {
+    new() {
+      super.new();
+    }
+  };
+  regress_20394_test_none_multi.main = function() {
+    new regress_20394_test_none_multi.C();
+  };
+  dart.fn(regress_20394_test_none_multi.main, VoidTodynamic());
+  // Exports:
+  exports.regress_20394_test_none_multi = regress_20394_test_none_multi;
+  exports.regress_20394_lib = regress_20394_lib;
+});