Revert "Remove @deprecated features."

pkg/observe/lib/src/change_record.dart

Index: pkg/observe/lib/src/change_record.dart
diff --git a/pkg/observe/lib/src/change_record.dart b/pkg/observe/lib/src/change_record.dart
index c3cb3b5f1bafda66592fb1967b434e1748cfb266..bb584e8f427aa2e35f0e9dc612a774094e0c21c8 100644
--- a/pkg/observe/lib/src/change_record.dart
+++ b/pkg/observe/lib/src/change_record.dart
@@ -10,6 +10,13 @@ abstract class ChangeRecord {}
 
 /** A change record to a field of an observable object. */
 class PropertyChangeRecord<T> extends ChangeRecord {
+  /**
+   * *Deprecated* use [name] instead.
+   * The field that was changed.
+   */
+  @deprecated
+  Symbol get field => name;
+
   /** The object that changed. */
   final object;
 
@@ -24,6 +31,13 @@ class PropertyChangeRecord<T> extends ChangeRecord {
 
   PropertyChangeRecord(this.object, this.name, this.oldValue, this.newValue);
 
+  /*
+   * *Deprecated* instead of `record.changes(key)` simply do
+   * `key == record.name`.
+   */
+  @deprecated
+  bool changes(key) => key is Symbol && name == key;
+
   String toString() =>
       '#<PropertyChangeRecord $name from: $oldValue to: $newValue>';
 }
@@ -46,6 +60,13 @@ class ListChangeRecord extends ChangeRecord {
     }
   }
 
+  /**
+   * *Deprecated* use [indexChanged] instead.
+   * Returns true if the provided index was changed by this operation.
+   */
+  @deprecated
+  bool changes(value) => indexChanged(value);
+
   /** Returns true if the provided index was changed by this operation. */
   bool indexChanged(otherIndex) {
     // If key isn't an int, or before the index, then it wasn't changed.