keep mixin and interface implementation info at runtime

lib/runtime/dart_runtime.js

 // 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.
 
 var dart, _js_helper;
 (function (dart) {
   'use strict';
 
   var defineProperty = Object.defineProperty;
   var getOwnPropertyDescriptor = Object.getOwnPropertyDescriptor;
@@ skipping 179 matching lines @@
   function copyProperties(to, from) {
     var names = getOwnPropertyNames(from);
     for (var i = 0; i < names.length; i++) {
       var name = names[i];
       defineProperty(to, name, getOwnPropertyDescriptor(from, name));
     }
     return to;
   }
   dart.copyProperties = copyProperties;
 
+
+  /** The Symbol for storing type arguments on a specialized generic type. */
+  dart.mixins = Symbol('mixins');
+  dart.implements = Symbol('implements')
+
   /**
    * Returns a new type that mixes members from base and all mixins.
    *
    * Each mixin applies in sequence, with further to the right ones overriding
    * previous entries.
    *
    * For each mixin, we only take its own properties, not anything from its
    * superclass (prototype).
    */
   function mixin(base/*, ...mixins*/) {
@@ skipping 12 matching lines @@
           mixin.prototype[mixin.name].call(this);
         }
         // Run base initializer.
         base.prototype[base.name].apply(this, arguments);
       }
     }
     // Copy each mixin's methods, with later ones overwriting earlier entries.
     for (var i = 0; i < mixins.length; i++) {
       copyProperties(Mixin.prototype, mixins[i].prototype);
     }
+    // Save mixins for reflection
+    Mixin[dart.mixins] = mixins;
     return Mixin;
   }
   dart.mixin = mixin;
 
   /**
    * Creates a dart:collection LinkedHashMap.
    *
    * For a map with string keys an object literal can be used, for example
    * `map({'hi': 1, 'there': 2})`.
    *
@@ skipping 97 matching lines @@
   // of some sort, assuming we keep around `dynamic` at runtime.
   dart.dynamic = Object.create(null);
 
   dart.JsSymbol = Symbol;
 
   // TODO(jmesserly): hack to bootstrap the SDK
   _js_helper = _js_helper || {};
   _js_helper.checkNum = notNull;
 
 })(dart || (dart = {}));