add @MirrorsUsed to observe/polymer/polymer_exprs pkgs

pkg/polymer_expressions/test/eval_test.dart

 // Copyright (c) 2013, 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.
 
 library eval_test;
 
 import 'dart:async';
 
+// NOTE: this import is unused, but we use it to cause all mirrors to be
+// enabled. The tests reflect on LinkedHashMap.length and String.length.
+import 'dart:mirrors';
+
 import 'package:polymer_expressions/eval.dart';
 import 'package:polymer_expressions/filter.dart';
 import 'package:polymer_expressions/parser.dart';
 import 'package:unittest/unittest.dart';
 import 'package:observe/observe.dart';
 
 main() {
 
   group('eval', () {
     test('should return the model for an empty expression', () {
@@ skipping 299 matching lines @@
             items.add(foo);
           },
           afterMatcher: (c) => c.iterable.contains(foo)
       );
     });
 
   });
 
 }
 
-class Foo extends Object with ChangeNotifierMixin {
+@reflectable
+class Foo extends ChangeNotifierBase {
   String _name;
   String get name => _name;
   void set name(String n) {
     _name = notifyPropertyChange(#name, _name, n);
   }
 
   int age;
   Foo child;
   List<int> items;
 
@@ skipping 49 matching lines @@
   mutate();
   // fail if we don't receive an update by the next event loop
   return Future.wait([future, new Future(() {
     expect(passed, true, reason: "Didn't receive a change notification on $s");
   })]);
 }
 
 // Regression test from https://code.google.com/p/dart/issues/detail?id=13459
 class WordElement extends ObservableBase {
   @observable List chars1 = 'abcdefg'.split('');
-  List filteredList(List original) => [original[0], original[1]];
+  @reflectable List filteredList(List original) => [original[0], original[1]];
 }