add logging support for exceptions

pkg/logging/test/logging_test.dart

Index: pkg/logging/test/logging_test.dart
diff --git a/pkg/logging/test/logging_test.dart b/pkg/logging/test/logging_test.dart
index 1af342f5ed173f8e5277af218c7262888690c315..a631e8c56106a66fcaa35256b27ee1b57bf188bf 100644
--- a/pkg/logging/test/logging_test.dart
+++ b/pkg/logging/test/logging_test.dart
@@ -228,6 +228,49 @@ main() {
         'SHOUT: 8']));
     });
 
+    test('logging methods store exception', () {
+      root.level = Level.ALL;
+      var rootMessages = [];
+      root.onRecord.listen((r) {
+        rootMessages.add('${r.level}: ${r.message} ${r.exception}');
+      });
+
+      root.finest('1');
+      root.finer('2');
+      root.fine('3');
+      root.config('4');
+      root.info('5');
+      root.warning('6');
+      root.severe('7');
+      root.shout('8');
+      root.finest('1', 'a');
+      root.finer('2', 'b');
+      root.fine('3', ['c']);
+      root.config('4', 'd');
+      root.info('5', 'e');
+      root.warning('6', 'f');
+      root.severe('7', 'g');
+      root.shout('8', 'h');
+
+      expect(rootMessages, equals([
+        'FINEST: 1 null',
+        'FINER: 2 null',
+        'FINE: 3 null',
+        'CONFIG: 4 null',
+        'INFO: 5 null',
+        'WARNING: 6 null',
+        'SEVERE: 7 null',
+        'SHOUT: 8 null',
+        'FINEST: 1 a',
+        'FINER: 2 b',
+        'FINE: 3 [c]',
+        'CONFIG: 4 d',
+        'INFO: 5 e',
+        'WARNING: 6 f',
+        'SEVERE: 7 g',
+        'SHOUT: 8 h']));
+    });

[gram, 2013/06/20 00:49:24]

It feels like this should be driven by the message list, splitting each message
on space and using that to drive the logging. You could use the same driver for
the previous test. Maybe just a TODO for now.

+
     test('message logging - no hierarchy', () {
       root.level = Level.WARNING;
       var rootMessages = [];