Revert "Make Comparable generic."

This reverts commit dd714db881a0ad63eaa1e5491e93dd8843eb5929.

R=lrn@google.com
BUG=

Review URL: https://codereview.chromium.org//12298027

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/logging@18657 260f80e4-7a28-3924-810f-c04153c831b5
diff --git a/lib/logging.dart b/lib/logging.dart
index 935b3ae..5e0a239 100644
--- a/lib/logging.dart
+++ b/lib/logging.dart
@@ -247,7 +247,7 @@
  * own level, make sure you use a value between those used in [Level.ALL] and
  * [Level.OFF].
  */
-class Level implements Comparable<Level> {
+class Level implements Comparable {
 
   // TODO(sigmund): mark name/value as 'const' when the language supports it.
   final String name;