fix #29544, mixins to a class with named constructors

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/utils.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 part of dart._runtime;
 
 /// This library defines a set of general javascript utilities for us
 /// by the Dart runtime.
 // TODO(ochafik): Rewrite some of these in Dart when possible.
 
 defineProperty(obj, name, desc) =>
@@ skipping 22 matching lines @@
   if (_trapRuntimeErrors) JS('', 'debugger');
   JS('', 'throw Error(#)', message);
 }
 
 getOwnNamesAndSymbols(obj) {
   var names = getOwnPropertyNames(obj);
   var symbols = getOwnPropertySymbols(obj);
   return JS('', '#.concat(#)', names, symbols);
 }
 
-safeGetOwnProperty(obj, String name) {
+safeGetOwnProperty(obj, name) {
   var desc = getOwnPropertyDescriptor(obj, name);
   if (desc != null) return JS('', '#.value', desc);
 }
 
 /// Defines a lazy property.
 /// After initial get or set, it will replace itself with a value property.
 // TODO(jmesserly): reusing descriptor objects has been shown to improve
 // performance in other projects (e.g. webcomponents.js ShadowDOM polyfill).
 defineLazyProperty(to, name, desc) => JS(
     '',
@@ skipping 63 matching lines @@
 }
 
 @JSExportName('export')
 exportProperty(to, from, name) => copyProperty(to, from, name);
 
 /// Copy properties from source to destination object.
 /// This operation is commonly called `mixin` in JS.
 copyProperties(to, from) {
   return copyTheseProperties(to, from, getOwnNamesAndSymbols(from));
 }