Revert "Remove @deprecated features."

pkg/observe/lib/src/observable_map.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;
 
 // TODO(jmesserly): this needs to be faster. We currently require multiple
 // lookups per key to get the old value.
 // TODO(jmesserly): this doesn't implement the precise interfaces like
 // LinkedHashMap, SplayTreeMap or HashMap. However it can use them for the
@@ skipping 21 matching lines @@
 
   MapChangeRecord(this.key, this.oldValue, this.newValue)
       : isInsert = false, isRemove = false;
 
   MapChangeRecord.insert(this.key, this.newValue)
       : isInsert = true, isRemove = false;
 
   MapChangeRecord.remove(this.key, this.oldValue)
       : isInsert = false, isRemove = true;
 
+  /// *Deprecated* compare [key]s instead.
+  @deprecated
+  bool changes(otherKey) => key == otherKey;
+
   String toString() {
     var kind = isInsert ? 'insert' : isRemove ? 'remove' : 'set';
     return '#<MapChangeRecord $kind $key from: $oldValue to: $newValue>';
   }
 }
 
 /**
  * Represents an observable map of model values. If any items are added,
  * removed, or replaced, then observers that are listening to [changes]
  * will be notified.
@@ skipping 97 matching lines @@
       });
       notifyPropertyChange(#length, len, 0);
     }
     _map.clear();
   }
 
   void forEach(void f(K key, V value)) => _map.forEach(f);
 
   String toString() => Maps.mapToString(this);
 }