package:observe fix various api issues

pkg/observe/lib/src/change_notifier.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 observe;
 
 /**
- * Base class implementing [Observable] object that performs its own change
- * notifications, and does not need to be considered by [Observable.dirtyCheck].
+ * Mixin and base class for implementing an [Observable] object that performs
+ * its own change notifications, and does not need to be considered by
+ * [Observable.dirtyCheck].
  *
  * When a field, property, or indexable item is changed, a derived class should
  * call [notifyPropertyChange]. See that method for an example.
  */
-class ChangeNotifierBase = Object with ChangeNotifierMixin;
-
-/**
- * Mixin implementing [Observable] object that performs its own change
- * notifications, and does not need to be considered by [Observable.dirtyCheck].
- *
- * When a field, property, or indexable item is changed, a derived class should
- * call [notifyPropertyChange]. See that method for an example.
- */
-abstract class ChangeNotifierMixin implements Observable {
+abstract class ChangeNotifier implements Observable {
   StreamController _changes;
   List<ChangeRecord> _records;
 
   Stream<List<ChangeRecord>> get changes {
     if (_changes == null) {
       _changes = new StreamController.broadcast(sync: true,
           onListen: _observed, onCancel: _unobserved);
     }
     return _changes.stream;
   }
@@ skipping 24 matching lines @@
   /**
    * True if this object has any observers, and should call
    * [notifyPropertyChange] for changes.
    */
   bool get hasObservers => _changes != null && _changes.hasListener;
 
   /**
    * Notify that the field [name] of this object has been changed.
    *
    * The [oldValue] and [newValue] are also recorded. If the two values are
-   * identical, no change will be recorded.
+   * equal, no change will be recorded.
    *
    * For convenience this returns [newValue]. This makes it easy to use in a
    * setter:
    *
    *     var _myField;
    *     @reflectable get myField => _myField;
    *     @reflectable set myField(value) {
    *       _myField = notifyPropertyChange(#myField, _myField, value);
    *     }
    */
   notifyPropertyChange(Symbol field, Object oldValue, Object newValue)
       => _notifyPropertyChange(this, field, oldValue, newValue);
 
   void notifyChange(ChangeRecord record) {
     if (!hasObservers) return;
 
     if (_records == null) {
       _records = [];
       scheduleMicrotask(deliverChanges);
     }
     _records.add(record);
   }
 }