implement mixins in subtype checks, more codegen fixes

test/browser/runtime_tests.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 assert = chai.assert;
 
 suite('generic', () => {
   "use strict";
 
   let generic = dart.generic;
@@ skipping 244 matching lines @@
     checkType(aaraw, aadynamictype);
     checkType(aaraw, AA$(dynamic, dynamic));
     checkType(aadynamic, aarawtype);
     checkType(aadynamic, AA);
   });
 
   test('void', () => {
     //checkType((x) => x, type((void _(x)) {}));
   });
 
+  test('mixins', () => {
+    let c = collection;
+    var s1 = new (c.SplayTreeSet$(String))();
+
+    checkType(s1, c.IterableMixin);
+    checkType(s1, c.IterableMixin$(String));
+    checkType(s1, c.IterableMixin$(int), false);
+
+    checkType(s1, c.SetMixin);
+    checkType(s1, c.SetMixin$(String));
+    checkType(s1, c.SetMixin$(int), false);
+  });
 });