package:observe fix various api issues

pkg/observe/lib/src/change_notifier.dart

Index: pkg/observe/lib/src/change_notifier.dart
diff --git a/pkg/observe/lib/src/change_notifier.dart b/pkg/observe/lib/src/change_notifier.dart
index 5e08f33f1091750e40c1ae166bdaa6f782003f67..a51fda6e8c4526396cda3e99ab02d5f31f985204 100644
--- a/pkg/observe/lib/src/change_notifier.dart
+++ b/pkg/observe/lib/src/change_notifier.dart
@@ -5,22 +5,14 @@
 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;
 
@@ -65,7 +57,7 @@ abstract class ChangeNotifierMixin implements Observable {
    * 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: