One more minor mixin fix

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.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.
 
 /// This library defines the operations that define and manipulate Dart
 /// classes.  Included in this are:
 ///   - Generics
 ///   - Class metadata
 ///   - Extension methods
 ///
@@ skipping 11 matching lines @@
 /// superclass (prototype).
 ///
 mixin(base, @rest mixins) => JS(
     '',
     '''(() => {
   // Create an initializer for the mixin, so when derived constructor calls
   // super, we can correctly initialize base and mixins.
 
   // Create a class that will hold all of the mixin methods.
   class Mixin extends $base {}
+  // Save the original constructor.  For ClassTypeAlias definitions, this
+  // is the concrete type.  We embed metadata (e.g., implemented interfaces)
+  // on this constructor and need to access that from runtime instances.
+  var constructor = Mixin.prototype.constructor;

[Jacob, 2017/05/19 14:31:27]

nit: let

   // Copy each mixin's methods, with later ones overwriting earlier entries.
   for (let m of $mixins) {
     $copyProperties(Mixin.prototype, m.prototype);
   }
+  // Restore original Mixin constructor.
+  Mixin.prototype.constructor = constructor;  
   // Initializer methods: run mixin initializers, then the base.
   Mixin.prototype.new = function(...args) {
     // Run mixin initializers. They cannot have arguments.
     // Run them backwards so most-derived mixin is initialized first.
     for (let i = $mixins.length - 1; i >= 0; i--) {
       $mixins[i].prototype.new.call(this);
     }
     // Run base initializer.
     $base.prototype.new.apply(this, args);
   };
   let namedCtors = ${safeGetOwnProperty(base, _namedConstructors)};
   if ($base[$_namedConstructors] != null) {
     for (let namedCtor of $base[$_namedConstructors]) {
       Mixin.prototype[namedCtor] = function(...args) {
         // Run mixin initializers. They cannot have arguments.
         // Run them backwards so most-derived mixin is initialized first.
         for (let i = $mixins.length - 1; i >= 0; i--) {
           $mixins[i].prototype.new.call(this);
         }
         // Run base initializer.
         $base.prototype[namedCtor].apply(this, args);
       };
+      $defineNamedConstructor(Mixin, namedCtor);
     }
   }
 
   // Set the signature of the Mixin class to be the composition
   // of the signatures of the mixins.
   $setSignature(Mixin, {
     methods: () => {
       let s = {};
       for (let m of $mixins) {
         if (m[$_methodSig]) $copyProperties(s, m[$_methodSig]);
@@ skipping 551 matching lines @@
 /// For example it can be called with `new SomeClass.name(args)`.
 ///
 /// The constructor
 defineNamedConstructorCallable(clazz, name, ctor) => JS(
     '',
     '''(() => {
   ctor.prototype = $clazz.prototype;
   // Use defineProperty so we don't hit a property defined on Function,
   // like `caller` and `arguments`.
   $defineProperty($clazz, $name, { value: ctor, configurable: true });
+
+  let namedCtors = ${safeGetOwnProperty(clazz, _namedConstructors)};
+  if (namedCtors == null) $clazz[$_namedConstructors] = namedCtors = [];
+  namedCtors.push($name);
 })()''');
 
 defineEnumValues(enumClass, names) => JS(
     '',
     '''(() => {
   let values = [];
   for (var i = 0; i < $names.length; i++) {
     let value = $const_(new $enumClass(i));
     values.push(value);
     Object.defineProperty($enumClass, $names[i],
         { value: value, configurable: true });
   }
   $enumClass.values = $constList(values, $enumClass);
 })()''');