Revert "Remove @deprecated features."

pkg/observe/lib/src/observable.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;
 
 /**
  * Represents an object with observable properties. This is used by data in
  * model-view architectures to notify interested parties of [changes] to the
  * object's properties (fields or getter/setter pairs).
@@ skipping 153 matching lines @@
    *   [Observable.dirtyCheck] instead.
    */
   void notifyChange(ChangeRecord record) {
     if (!hasObservers) return;
 
     if (_records == null) _records = [];
     _records.add(record);
   }
 }
 
+/**
+ * *Deprecated* use [Observable.notifyPropertyChange] instead.
+ *
+ * This API should not be used as it creates a
+ * [PropertyChangeRecord] without oldValue and newValue.
+ *
+ * Notify the property change. Shorthand for:
+ *
+ *     target.notifyChange(new PropertyChangeRecord(target, name, null, null));
+ */
+@deprecated
+void notifyProperty(Observable target, Symbol name) {
+  target.notifyChange(new PropertyChangeRecord(target, name, null, null));
+}
+
 // TODO(jmesserly): remove the instance method and make this top-level method
 // public instead?
 _notifyPropertyChange(Observable obj, Symbol field, Object oldValue,
     Object newValue) {
 
   if (obj.hasObservers && oldValue != newValue) {
     obj.notifyChange(new PropertyChangeRecord(obj, field, oldValue, newValue));
   }
   return newValue;
 }