Also generate error when autogenerating stack traces (fix #25)

lib/logging.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  */
 library logging;
 
 import 'dart:async';
 import 'dart:collection';
@@ skipping 142 matching lines @@
   void log(Level logLevel, message,
       [Object error, StackTrace stackTrace, Zone zone]) {
     if (isLoggable(logLevel)) {
       if (message is Function) message = message();
       if (message is! String) message = message.toString();
       if (stackTrace == null && logLevel >= recordStackTraceAtLevel) {
         try {
           throw "autogenerated stack trace for $logLevel $message";
         } catch (e, t) {
           stackTrace = t;
+          if (error == null) error = e;
         }
       }
       if (zone == null) zone = Zone.current;
 
       var record =
           new LogRecord(logLevel, message, fullName, error, stackTrace, zone);
 
       if (hierarchicalLoggingEnabled) {
         var target = this;
         while (target != null) {
@@ skipping 169 matching lines @@
   /** Zone of the calling code which resulted in this LogRecord. */
   final Zone zone;
 
   LogRecord(this.level, this.message, this.loggerName,
       [this.error, this.stackTrace, this.zone])
       : time = new DateTime.now(),
         sequenceNumber = LogRecord._nextNumber++;
 
   String toString() => '[${level.name}] $loggerName: $message';
 }