Add some additional debugging prints to the mac os watcher.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//146693014

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/watcher@32139 260f80e4-7a28-3924-810f-c04153c831b5

pkgs/watcher/lib/src/directory_watcher/mac_os.dart

diff --git a/pkgs/watcher/lib/src/directory_watcher/mac_os.dart b/pkgs/watcher/lib/src/directory_watcher/mac_os.dart
index ba0ede4..e3efa2d 100644
--- a/pkgs/watcher/lib/src/directory_watcher/mac_os.dart
+++ b/pkgs/watcher/lib/src/directory_watcher/mac_os.dart
@@ -109,7 +109,7 @@
 
   void close() {
     if (MacOSDirectoryWatcher.logDebugInfo) {
-      print("[$_id] watcher is closed");
+      print("[$_id] watcher is closed\n${new Chain.current().terse}");
     }
     if (_watchSubscription != null) _watchSubscription.cancel();
     if (_initialListSubscription != null) _initialListSubscription.cancel();
@@ -468,6 +468,10 @@
 
   /// Emit an error, then close the watcher.
   void _emitError(error, StackTrace stackTrace) {
+    if (MacOSDirectoryWatcher.logDebugInfo) {
+      print("[$_id] emitting error: $error\n" +
+          "${new Chain.forTrace(stackTrace).terse}");
+    }
     _eventsController.addError(error, stackTrace);
     close();
   }