Make type signature consistent with class Object

BUG=
R=sigmund@google.com

Review URL: https://codereview.chromium.org//823613004
diff --git a/lib/logging.dart b/lib/logging.dart
index 5f4bc2b..dc83d84 100644
--- a/lib/logging.dart
+++ b/lib/logging.dart
@@ -278,7 +278,7 @@
   static const List<Level> LEVELS = const
       [ALL, FINEST, FINER, FINE, CONFIG, INFO, WARNING, SEVERE, SHOUT, OFF];
 
-  bool operator ==(Object other) => other is Level && value == other.value;
+  bool operator ==(other) => other is Level && value == other.value;
   bool operator <(Level other) => value < other.value;
   bool operator <=(Level other) => value <= other.value;
   bool operator >(Level other) => value > other.value;