package:observe fix various api issues

pkg/polymer/lib/src/instance.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.
 
 part of polymer;
 
 /**
  * Use this annotation to publish a field as an attribute. For example:
  *
  *     class MyPlaybackElement extends PolymerElement {
@@ skipping 880 matching lines @@
     super.close();
   }
 
   void boundValueChanged(newValue) {
     _lastValue = newValue;
     _target.setField(_property, newValue);
   }
 
   void _propertyValueChanged(List<ChangeRecord> records) {
     for (var record in records) {
-      if (record.changes(_property)) {
+      if (record is PropertyChangeRecord && record.name == _property) {
         final newValue = _target.getField(_property).reflectee;
         if (!identical(_lastValue, newValue)) {
           value = newValue;
         }
         return;
       }
     }
   }
 }
 
@@ skipping 23 matching lines @@
 
 final Expando _shadowHost = new Expando<Polymer>();
 
 final Expando _eventHandledTable = new Expando<Set<Node>>();
 
 /**
  * Base class for PolymerElements deriving from HtmlElement.
  *
  * See [Polymer].
  */
-class PolymerElement extends HtmlElement with Polymer, ObservableMixin {
+class PolymerElement extends HtmlElement with Polymer, Observable {
   PolymerElement.created() : super.created() {
     polymerCreated();
   }
 }